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Benjamin Barry is an advertising executive and ladies' man who, to win a big campaign, bets that he can make a woman fall in love with him in 10 days.

Benjamin Barry is an advertising executive competing with two female co-workers for a major campaign for a diamond merchant. He cuts a deal with his competitors that the account is his if he can make a woman of their choice fall in love with him in 10 days. In comes Andie Anderson who, in turn, is writing a story on how to lose a guy in 10 days as a bet with her boss to be allowed to write more substantial stories. With a hidden agenda in each camp, will either party be able to complete their mission?—Peter Brandt Nielsen

Benjamin Barry is an advertising executive and ladies' man who, to win a big campaign, bets that he can make a woman fall in love with him in 10 days. Andie Anderson covers the "How To" beat for "Composure" magazine and is assigned to write an article on "How to Lose a Guy in 10 days." They meet in a bar shortly after the bet is made.—Moe

A ladies man bet his friends that he can get a woman to fall in love with him in 10 days, but unbeknownst to him, the woman he's dating is actually a magazine columnist working on a new column called "How to Lose a Guy in 10 Days", and she's doing everything she could to drive the guy she's dating crazy.

Benjamin, an ad executive, is trying to land a big account, only his boss thinks that it needs a feminine touch, so he considers giving it to a couple of female execs. Benjamin makes a wager with them that if he can get a woman to fall in love with him he gets the account. He lets the female execs choose the girl. They choose Andie, a writer for Composure magazine whom they had met earlier and learned she is doing an article called "How to Lose a Guy in 10 Days". Knowing that she's going to be impossible, they don't tell him that. Ben tries his best to woo her while she does her best to drive him away.—rcs0411@yahoo.com

Andie Anderson (Kate Hudson) is a writer who works for a magazine called Composure as the "How to..." woman. She is bored and wishes she could write more about important things, such as politics, economics, religion, poverty; stuff she cares about. She soon finds herself writing an article called "How to Lose a Guy in 10 Days". The idea comes about when Andie's friend, Michelle (Kathryn Hahn), experiences a minor breakdown after yet another break-up. Using her friend as inspiration, Andie reveals how she will actually start dating a guy and drive him away but 'only using the classic mistakes women make'.

At the same time, advertising executive Benjamin Barry (Matthew McConaughey) is striving for a pitch to advertise diamonds and explains to his boss and co-workers how "a woman in lust wants chocolate, a woman in love wants diamonds." Questioning what Ben would know about love, Ben bets he could make any woman fall in love with him if he wanted to, and so the bet arises. If he can make any woman fall in love with him before the upcoming company ball, in just 10 days, he can be in charge of the advertising for the new diamond company.

Ben's rival co-workers, Judy Spears (Michael Michele) and Judy Green (Shalom Harlow), who were at Composure Magazine earlier and are aware of Andie's new assignment, conspire to have Andie and Ben meet that night and start their quests. Fortunately, that night Andie and Ben happen to be in the same place and as Judy and Judy refer to her as "the blond with the pretty smile", Ben thinks it is a done deal.

Neither Andie nor Ben reveals their true intentions. Andie works hard to make Ben break up with her in order to go about completion of her article, however, Ben continues to stick around in the hope of making her fall in love with him. Andie goes on to get Ben knocked out at a chick flick film, rapidly moves her stuff into his apartment, acts overly possessive and sensitive at all times, ruins boys' poker night for him and his friends and takes him to a Celine Dion concert when he was under the assumption, he was going to see a New York Knicks basketball game, which Andie had wanted.

Ben stays with her despite everything, and after coming very close to a break-up they attend couples counseling, led by Andie's friend Michelle. They agree, as a solution to their 'problems' they will go to see Ben's family in Staten Island for the weekend. While holidaying together, Ben and Andie begin to form a genuine bond; playing card games with the family, learning to ride Ben's motorcycle and upon arrival home Ben even refers to Andie as 'his girlfriend'.

Andie tries to explain to boss Lana (Bebe Neuwirth) that she cannot go ahead with writing and publishing this article as she has "really got to know this guy", but Lana remains insistent upon it. Around the same time, Andie and Ben go to the company ball together where Ben's boss, Phillip (Robert Klein) meets Andie and tells Ben that he "met her, she loves you, you win". Seeing Ben's good news, Spears and Green are instantly envious and set about to ruin it for their co-worker.

They tell his close worker colleagues, Tony (Adam Goldberg) and Thayer (Thomas Lennon) Andie knew about the bet all along and was playing along in order for Ben to win. Almost instantly, Tony and Thayer rush to Andie's side and beg her to keep quiet, when they do not realize she is still blissfully unaware. Almost simultaneously, Ben finds out about Andie's true intentions as they are revealed to him by boss Lana - who is unaware of Ben's role in her How-to Girl's article.

Upon finding out, Andie attempts to humiliate Ben by getting on stage and telling all he has prepared a "special treat" and is to sing a song. In an attempt to then leave, Ben reveals they have prepared a "duet" and instructs his friends to not let her leave the room. They go on to sing a poor version of You're So Vain, originally by Carly Simon described as "one of their personal favorites" which they alternatively sang as: A: "Ben Barry you're so vain, you probably think this song is about you, don't you, don't you! You fooled me to win a bet, you should feel ashamed". B: "Look, You took me to a god damn Celine Dion concert, you made me miss the big game". A: "Oh, Smart Guy's a rhymer, well do we want everybody to know your love making is lame". B: "Maybe because you named my penis, you named my penis, you named my penis after a dame."

They go their separate ways before Ben is shown Andie's article and encouraged to read it. She explains in it how she 'lost the one man she ever fell for' and when he hears she quit her job at Composure and was on her way to Washington for an interview he chases her and stops her. Calling her bluff and saying that she is running away, they reveal their true feelings for each other, and the film ends as Ben instructs the taxi driver to return Andie's belongings to her home and they kiss.