On his way to Bramson College, Stephen Parker’s car breaks down on the Pacific Coast Highway. His friend, Andy Roselli, and Andy’s girl friend, Jackie, pick him up and take him to their beach house, where they are hosting a party. Stephen throws himself into campus life. While playing tennis, he sees a beautiful girl, Shelly Anderson, on the next court and loses concentration. Seeing her again in biology class, he introduces himself, but becomes tongue-tied. He doodles Shelly’s name in his notebook. Whenever he tries to approach, Shelly’s jock boyfriend, Brad, warns him to stay away. Worse, Stephen’s tennis instructor throws him off the team for being inattentive. Stephen confides to Andy that if he does not get close to Shelly, he will lose his mind and his scholarship. When Angela, Shelly’s tennis team partner, sprains her ankle, Andy suggests that if Stephen were on the women’s team, he could spend all his time with Shelly. Stephen agrees, and with Jackie’s help he puts together a female wardrobe, dons a wig, and applies makeup. Andy coaches him on how to drink, eat, walk, and laugh like a girl, while Jackie supplies him with a brassiere and a pair of “falsies.” Signing up for the team as “Stephanie Brown,” Stephen easily qualifies despite his awkwardness at feigning femininity. Sitting in the bleachers, Andy telephones his bookie to bet on Bramson’s women’s team for the upcoming Saturday tennis match. Shelly Anderson introduces herself to “Stephanie,” admires “her” tennis backhand, and thinks they would make a great doubles pair. Over coffee, Stephen has to keep correcting himself. When he blurts out how beautiful she is, Shelly shyly admits her ears are too big, but that looks are not everything. Brad comes into the commissary, sits down, and thinks he knows Stephanie from somewhere. He propositions Shelly with the idea that since her roommate, Angela, is not coming back to school, maybe he can move in with her. Shelly reminds him that the dorm is not co-ed, and she has already asked Stephanie to move in. Disappointed, Brad leaves, and Shelly admits that Brad's sexual attraction to her would make it impossible for them to live together. While Stephen packs his things in his dorm room, Jackie hacks into the college computer and registers Stephanie Brown as an American transfer student from Geneva, Switzerland. Thinking that Stephen’s infatuation with Shelly will end when he realizes she is not very smart, Jackie checks Shelly’s grades and is surprised that she has a high grade-point average. Andy telephones his bookie and jumps his bet by to $20,000 on the Bramson women’s tennis team. After Stephanie moves into Shelly’s dorm room, Brad telephones to ask if Stephanie wants to date one of his friends. Distracted by something else, Stephanie says “super,” sealing the date. Stephen awakens at 6:00 a.m. to prepare himself before Shelly gets up. He fumbles into a pair of pantyhose, ripping them. He runs to Andy’s beach house because he needs his friend’s assistance with his class schedule, which Andy has written down. Both Stephen and Stephanie have classes, often one after another, so each morning he must awaken as Stephanie, run to Andy's to change into Stephen, run back to school to attend class, run back to Andy’s to change back into Stephanie, and so on. Before long, he becomes groggy and inattentive in class. He also exercises with the women’s tennis team. In their dorm room, Shelley asks Stephanie to rub cream on her shoulders, which forces Stephen to check his self-control. She reminds Stephanie that Brad has set “her” up with Stanley, but Stephanie begs off because “she” is still getting over another guy. When they discuss Shelly’s relationship with Brad, Stephanie feels he is too aggressive. Shelly confesses she does not “enjoy sex that much,” and Stephanie tells her that a man who really loves her would treat her special and touch her as if she were valuable. Becoming excited, Stephen excuses himself. Andy and Jackie run a business writing term papers for students out of the beach house, so when Stephen informs Andy that “Stephanie” has a physical exam tomorrow, Andy agrees to “fix everything.” At Dr. Duncan’s office, Stephanie is given a robe and sent to a dressing room. “She” claims to have a religious objection, but the doctor overrules it and tells Stephanie to sit down and put her feet in the stirrups. As the doctor greases a vaginal probe, Andy suddenly rushes in wearing a hardhat, claiming to be an earthquake specialist, and ransacks the office. In desperation, Dr. Duncan signs Stephanie’s form to get rid of her. At the tennis courts, after Stephanie beats Shelly, another player named Marge asks Stephanie if she takes steroids in order to hit the ball so hard. Marge mentions to Carla, another coed, that there is “something really strange” about Stephanie. That evening, Shelly takes Stephanie to Carla and Marge’s dorm room for “beauty night,” so that they can give each other beauty treatments. The girls tweeze Stephanie’s eyebrows and remove facial hair with hot wax. Later, Brad and his friend, Stanley, take Shelly and Stephanie to the beach. Stanley, a large football player, lifts Stephanie in his arms, coddles her, and cannot stop himself from groping her. He takes takes Stephanie for a stroll, but it turns into a run as Stephanie escapes his clutches. Later, as Shelly enters their bathroom while Stephen takes a bath, he uses a rubber ducky to hide his manhood. At bedtime, Shelly confides that dating Brad has been a mistake. When she asks about the boy Stephanie is still brooding over, “she” identifies him as a Bramson student named Stephen Parker who is very sensitive and sweet. Shelly remembers Stephen from her biology class, and admits she finds him attractive. The next day, in biology class, Shelly keeps looking at Stephen and introduces herself after class. They discuss Stephanie, and when Stephen asks Shelly for a Friday afternoon date, she accepts. Later, Stephanie meets Shelly for lunch, and Stella confesses she is interested in Stephen and apologizes for making a date with him. Stephanie assures Shelly that she is over Stephen and wants her to have a good time. On Friday, Stephen takes Shelly on a picnic, walks her home after dark, and kisses her goodnight. Shelly would like to ask him up to her room, but Stephanie might be there. The next day, Shelly returns from class early and catches Stephanie urinating, standing up, into the toilet. Stephen pulls off the wig and tells Shelly he loves her, but she slaps him and orders him to leave. Mr. and Mrs. Parker arrive at Andy’s place unannounced to surprise their son, and are shocked as Stephen walks in dressed as a girl and carrying all his feminine belongings. Andy saves the day by asking Stephen how the variety show auditions went. Stephen confides to Andy that Shelly knows who he is. When his parents take him out to dinner, Stephen sees Brad and Shelly drive by. At tennis practice, the coach asks Shelly where her partner is. In English class, Professor Lucci tells Stephen he must turn in his literature paper in tomorrow or he will lose his scholarship. He decides to use a paper about Charles Dickens’s use of orphans in his novels that “Stephanie” wrote for a sociology class. At the library, when Shelly sees Stephen talking with Carla, she gets him alone and admits she needs Stephanie for the tennis team, or else they cannot win. Stephen tells her he will think about it. Later, however, Andy convinces Stephen to rejoin the women’s tennis team because his bookie will take everything he has if the team loses. Stephen becomes angry, realizing that Andy’s scheme to pass him off as Stephanie was about money, not about his love for Shelly. Stephen picks up a letter that arrived at the house for him, glances at it, tosses it away, and storms out of the house. Andy picks up the letter and reads it: According to James Butler, the college dean, Stephen is being brought up in front of the student judiciary committee for plagiarizing a fellow student’s psychology paper for English class, and both Stephen and Stephanie must be in his office the following afternoon. The next day, Stephen goes before the committee and claims he wrote the paper. Andy shows up dressed as Stephanie Brown, and when a member of the faculty suspects that Stephanie’s appearance has changed, Shelly embraces “Steffy” and vouches for her identity. When Stephanie confesses to copying Stephen’s paper in the library, charges against Stephen are dismissed. The next day, during tennis finals, Fillmore College stars Adams and Greta Schvitz are ready for the deciding match. Suddenly, Stephanie shows up and joins Shelly. Stephen professes his love, and Shelly returns the sentiment. When Andy Roselli discovers that Ellis Crawford, a man sitting in front of him, is an agent from the International Women’s Tennis Circuit, he introduces himself as Stephanie’s manager. Ellis wants to sign contracts with both Shelly and Stephanie. When Shelly and Stephanie win, everyone in the bleachers is shocked to see them passionately kiss.