Last fall, on the eve of his 33rd birthday, my pal Ian bumped into an old college buddy at a hockey game. Though Mr. Waybackwhen wasn't exactly looking red-carpet-ready, having put on a few pounds, he gave Ian grief about his shaved head, facial hair, and clothes: "Ha ha, dude, what have you been doing to yourself?"

As the two parted, Ian pointed his trusty finger-pistol at his back and pulled the trigger. And just like that, his former classmate was dead to him.

Back at home, Ian flipped through his Rolodex and kept right on firing. One after another, he yanked the cards of people he concluded were draining his life force. He nuked a dozen guys from his inner circle—and in the process administered an invigorating shot of self-affirmation. "It was the best birthday present I ever gave myself," he says.

Call it a top-to-bottom emotional housecleaning—or a heartless ploy to cut loose the losers—but the friend purge is a productive and healthy exercise for any guy in his mid-30s to early 40s. Sociologists have long noted that men tend to rein in their circle of confidants as they settle into what researchers call a "new life-cycle stage"—a seat in the corner office, say, or the double whammy of marriage plus mortgage. With each new stage you add a new, tighter circle.

So why not just leave the old circles behind? That's what Cameron Hayduk did. "It was like quitting a job I didn't like," says the 40-year-old camera technician, recalling how he pushed the delete key on a half-dozen sorta buddies one summer day five years back. "Friendships shouldn't feel like an obligation," he says. And so he stopped calling back that female pal who left long, whiny voice mails, and that guy who always needed to borrow 20 bucks until Friday. He also auto-trashed the e-mails from that obnoxious social climber who was constantly chasing a line, a name, a number, an angle.

Hayduk decided to go even further: He would add no new friends without first running a kind of inner-voice background check. "Now I assess the quality of the potential friendship," he explains. "I ask myself, 'Will there be balance? Will there be give-and-take?' Sometimes it almost feels a little too academic, but it's necessary."

That's because these days professional guys have a lot going on. The average American man works 46 hours a week (51 if he's a dad). And according to a 2002 study from the Families and Work Institute in New York, the average working father has a scant 1.3 hours of personal time a day.

So how far should a cleansing go? Sociologists debate how many friends the typical man has, because the term can be broad. But, says Robert Milardo, a professor of family relations at the University of Maine, "if you ask the average adult male how many people he knows whose opinions of his life matter to him, the answer is about five."

Even five friends may be three too many for you—the right number is however many you can handle without getting dragged down. Think of your group of friends as a stock portfolio: You want to hang on to the blue chips and dump the underperformers. Don't send them Christmas cards, and for God's sake don't cc them on the jpegs of your new puppy.

And don't stop there. To really clean house, you may need to rethink your whole routine, says Rebecca Adams, a professor of sociology at the University of North Carolina at Greensboro. "If someone wants to purge his friendships, he should just change his everyday pattern of behavior so he doesn't encounter these guys," she says. If you're still a regular at the corner bar, the one frequented by a bunch of guys you culled, then you haven't really culled them.

Besides, once you're free of the dead weight, you won't need drinking buddies. You'll be drunk on your newfound freedom.

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