Andie Anderson is a columnist for the women's magazine
Composure in New York. As the writer of a series of "How to" articles, she is dissatisfied with her work and wishes to write about more serious issues. When her friend Michelle experiences yet another breakup, Andie is inspired to write an article on "How to Lose a Guy in 10 Days". She will begin dating a man and attempt to drive him away "only using the classic mistakes women make". Meanwhile, advertising executive Benjamin Barry is looking to branch out from his usual remit of beer and sports campaigns by leading a prestigious ad campaign for a diamond company. Ben meets his boss Phillip Warren, and rival coworkers Judy Spears and Judy Green at a bar. To prove he is capable of pitching to women, Ben wagers that he can make any woman fall in love with him. Phillip agrees that if he can achieve this by the company ball in 10 days, he will get to lead the diamond campaign. Spears and Green, who were at
Composure magazine offices earlier that day and know about Andie's planned article, pick her as the woman for the bet. Ben and Andie start their relationship, neither revealing their true intentions. Soon, Andie kicks off a series of actions to drive Ben away, including making him miss the final moments of a Knicks game, creating a scrapbook of their future children, naming his penis Princess Sophia, and stocking his apartment with feminine hygiene products, stuffed toys, pink coverings, a not-yet-housebroken puppy, and a "love fern". During a boys' poker game night Andie arrives unannounced and behaves outrageously, driving Ben to finally break up with her, to her relief. However, Ben's friends Tony and Thayer push him to stay the course, proposing couple's therapy. Ben chases after Andie and she reluctantly agrees to continue the relationship. Andie has Michelle pose as a therapist and together they criticize Ben, who placates them by offering to introduce Andie to his family in
Staten Island that weekend. During the trip, Andie finds she truly likes his family, and is moved when Ben's mother asks her not to break his heart. Ben and Andie begin to form a genuine bond. On the tenth day Andie and Ben go to the company ball together. Phillip meets Andie, and later tells Ben that he "met her, she loves you, you win". To sabotage Ben, Spears and Green tell Tony and Thayer that Andie knew about the bet all along and was playing along to help Ben win. Tony and Thayer ask Andie to keep quiet, unwittingly making her aware of the bet. At the same time, Andie's boss, Lana, unaware of Ben's role, tells him about Andie's article. After Andie attempts to humiliate Ben in front of everyone at the party, he responds in kind. The pair argues on stage and break up. Tony shows Andie's subsequent article to Ben, in which she writes how she "lost the only guy I've ever fallen for". When he goes to see her, he discovers she has quit her job at 'Composure', as Lana still refuses to let her write about serious topics, and is on her way to Washington, D.C., for a job interview. Ben chases after her taxi and gets Andie to pull over. He asks her if what she wrote in the article was true, and when she says yes, accuses her of running away. They reveal their true feelings for each other and kiss. ==Cast==