If you're anxiously reading this article, you may already have it.
Oh, relax. It’s not a johnson-shrinking virus. "Small penis syndrome" is a psychological condition in which a man thinks his manhood is too small, even though he's really on par with the rest of mankind.
Is my penis size normal? That age-old question was addressed by British researchers in a recent study published in BJU International. Their findings, in a nutshell (or two): 63 per cent of men complained of having inferior hardware - but none of them was smaller than normal!
What is the average penis size? Measuring erect, between 5.5 and 6.2 inches long and 4.7 to 5.1 inches around - and don’t even think about measuring at your desk.
Does penis size matter to women? If you're still worried, consider that 85 per cent of women reported they were happy with their partner’s size.
Okay, British researchers are one thing. But what do real women think about penis size and what do they think think is the ideal penis size?
We asked two of our favourite women, Nicole Beland, former "Girl Next Door," and Dr Debby Herbenick, the Men's Health "Sex Professor," for their take on penis size.
"Yes, we care about the size of a man's penis," Beland says. "But when it comes to sexual satisfaction, it's pretty far down on our list of priorities."
Do women like big penises? Not necessarily. Large penises don't equal an instant orgasm. In fact, penis sizes that skew large can deter women's orgasms, Herbenick says. "Women find it difficult to orgasm, and oral sex and hand stimulation are often more effective, as are vibrators," she says. "It's not personal—it's just how some women's bodies work."
The biggest problem with large penises, the women say, is that they're often attached to even bigger dicks.
"There's nothing worse than a guy who thinks he has a HUGE penis and is therefore God's gift to the ladies," Beland says. "That kind of guy thinks that getting an erection is pretty much all the effort he has to put into sex. The chances that the women he sleeps with are having orgasms? Slim to none."
Dr Ian Kerner, sexologist and author of She Comes First, says we should worry more about her pleasure than our size.
"Usually when women complain about a small penis, it's also that they're not having orgasms," Kerner says. "If they’re orgasming, it'll matter a hell of a lot less what size your penis is."
For the truly tiny or even those paranoid normal guys, Kerner recommends "pressing instead of thrusting in missionary position, or trying woman-on-top," both of which maximize clitoral stimulation.
Beland suggests these positions: "Place her legs on your shoulders during missionary position, enter her from behind when she's on all fours, or, when she's on top, put a pillow under your butt to raise up your pelvis."
The British research (really just a review of previous studies) confirmed that women do indeed prefer a thick penis. The reason: "The greatest number of nerve endings are in the lowest part of the vagina," Nicole says. "So when a thick penis pushes against the labia and lower vaginal walls, it provides intense, pleasurable sensation.
"But men with thinner penises can provide a similar experience by penetrating in the positions described above or moving his hips in a circular motion while thrusting."
Why are men so worried about penis size? Part of the reason is pornography - 21st century man has seen plenty of prodigious penises on his screen. Most women don’t want that.
"When women watch male porn stars humping away like lobotomized underwear models," Nicole says, "it's almost always with a cringing, confused expression."
"Getting pummeled with a giant penis is painful, not fun. The majority of women don't consider bouncing up and down on a Poland Spring bottle to constitute great sex."
Herbenick, a researcher at Indiana University, says penile worries arise from "cultural myths and stereotypes about penis size that stem from television, movies, jokes told among friends, and advertising messages from companies that present false information about penis size in order to sell products that probably don’t even work."
Dr Lou Paget, author of The Great Lover Playbook, said point of view matters - literally.
"The majority of men compare themselves to something they see in adult material. They haven’t seen another man's penis up close," she says. "But women see them all the time. And we see a whole range of sizes.
"Men only see themselves, and look at a different angle than women - looking down."
In other words: Your penis looks bigger to women than it does to you.
And don’t forget that there’s a lot more to sexual and relationship satisfaction than penis size and positions. Like communication, Herbenick says: "Trust and believe your partner if she says, 'Honey, you’re fine' or 'I like you just how you are' rather than second-guess yourself."
The irony is that men spend so much time thinking about their anatomy when they should be thinking about hers. "It's a man's knowledge of female anatomy and ability to stimulate a woman in all the right ways that determines whether or not we’re happy in bed," Nicole says.
And don’t forget foreplay. "Twenty minutes of erotic foreplay with a guy who has a penis the size of a Sharpie will be far hotter than 2 minutes of sloppy groping from a dude with a johnson the size of a flashlight," Beland says.
And finally, guess what really matters? Don’t groan - it's personality.
"Of course it’s more important than any physical aspect of a man’s body," Nicole says. "Any woman who thinks otherwise isn't worth dating."