The movie is not very high-rated, having a 38% freshness rating at Rotten Tomatoes.
Tagline: One man is about to do the unthinkable. No sex. Whatsoever. For... 40 DAYS AND 40 NIGHTS.
Realizing that Lent is about to start, Matt tells John that he's going to do without sex for 40 days and 40 nights. This, he concludes, will force him to get over Nicole and cure his problem. John warns Matt that celibacy is not easy.
Matt and his roommate, Ryan (Paulo Costanzo), are co-workers at a dot-com company in San Francisco. Ryan tells everyone about Matt's plan to do without sex, and an office pool is started, and everyone in the office gets in on it.
After about six days of being productive and happy, Matt goes out and does his laundry. At the Laundromat, he meets a very pretty girl named Erica (Shannyn Sossamon), who works for Cyber Nanny, a search engine that keeps children from finding porn on the Internet. Matt and Erica make plans to come back and see each other next week.
Meanwhile, back at the office, the women Matt works with are trying to get him to crack: Two girls make out with each other in front of Matt while another girl (Monet Mazur) sits on a copier with her legs spread and photocopies her buttocks for Matt. Matt is strong, though, and doesn't give in to temptation.
When Matt and Erica do their laundry again, they make plans to go out on a date. Matt takes her on a bus ride all around the city, and rather than kiss her goodnight at the end of the evening, he high-fives her and falls backward off some stairs. The next day at work, Matt finds out about the office pool. Worse yet, it turns out that a guy at work set up a website about Matt and his vow of chastity. Even worse, Matt sees that it's been protected by Cyber Nanny, and realizes that Erica must know about his abstinence. He goes to her office, where he finds out that she's seen the site, and she's not too happy about it.
Matt and Erica go out to dinner a few nights later, after Erica's cooled down, and Nicole and her new fiancé are there. Matt introduces Nicole to Erica, and Erica realizes that Matt's celibacy is a result of his breakup with Nicole. Matt lies and tells her that it's not true. Erica, sick of Matt's lies, leaves the restaurant.
Matt's co-workers are getting desperate to get Matt to have sex, and one guy puts some crushed Viagra into Matt's orange juice. However, their boss Jerry (Griffin Dunne) accidentally ends up drinking it instead and goes off to the bathroom to masturbate. Another co-worker, Duncan, finds Matt hiding in a supply closet, shaking and sweating. Duncan agrees to cut him in for $9,000, 1/2 of the pool money he would win that day, if he caves in. He gives Matt a dirty magazine and convinces him to go into the bathroom and masturbate. Matt's about to but, overhearing Jerry masturbating in the next stall over, is so turned off that he climbs out the bathroom window and runs to Erica's house.
Erica and Matt have a very erotic encounter without touching each other. Somehow, Erica actually has an orgasm, then she falls asleep and Matt goes home.
On his way to work the next day, Matt hallucinates that every woman he sees is naked. He goes to John's office at the church and finds him making out with a nun. At first, Matt thinks it's another hallucination, but John couldn't remain celibate and decides to take a sabbatical from the seminary.
Matt goes to work and starts daydreaming about his romantic encounter with Erica. A co-worker wakes him up and tells him to get into the conference room for a meeting with an important client. As Matt walks into the conference room, each of his co-workers stares at his crotch in horror and amazement. Unbeknownst to Matt, he enters the conference room with an erection, and Duncan points it out to Matt and Jerry tells him to go home for the day.
Nicole comes by the apartment to say that she has broken up with her fiancé. She wants Matt back, and tries to make a move on him. Matt, however, turns her down and makes her leave the apartment. Nicole leaves, saying that Matt's new-found assertiveness makes him even hotter. At the Café, she finds out about the pool and bets $3,500 on the last day that she can get him to break.
In a scene which caused much criticism, Matt is handcuffed to his bed so that he won't be able to do anything (i.e. masturbate) to ruin his vow, which is ending that night. He falls asleep and has an erotic dream, but when he wakes up, Nicole is raping him. It seems she's just won the pool and, as Nicole is leaving, Erica arrives. She wrongly thinks Matt has cheated on her, and instead of hearing his side of the story she storms off, leaving him handcuffed to the bed posts.
Matt puts together a little box of reminders of their relationship and leaves it with Erica's roommate. Erica looks at the box, has a change of heart, and goes to the Laundromat. Matt shows up, and they kiss passionately, as the camera pans out.
After which, the movie opens back up to a scene with Matt's friends playing video games and listening to Matt and Erica have sex with loud music. While the men bet money on how long the couple's sex will last (or if it's even possible for their sex to be so long), Matt comes back down to pick food from the refrigerator (possibly for Sexual fetishism) and kicks them out. The men, after being kicked out, bet on Matt's life due to the thought of dying from too much sex.