I've always been suspicious of small secretive groups with strange rituals, perhaps because my dad, an ardent Freemason, forced me to listen as he memorised the various hokum incantations of the men who believe God resembles Norman Foster with his trouser leg rolled up. The one thing that kept me awake was the frisson of excitement that if I were one day to reveal any of these solemn secrets I might forfeit my life. Whoa. Scary.

Now I have discovered a weird alternative universe of my own: internet gay dating. Like the Ayrshire lodge of the Freemasons, it is strictly men only, and it certainly helps if you're drunk. But, thankfully, there is very little emphasis on good works, and no one runs a tombola.

I had toyed with gay dating before, when I first joined AOL a few years ago. But since its gay site rejoices in the name "Utopia Lesbian and Gay Village", I didn't have high hopes, especially when I discovered that each of the gay chatrooms was hosted by a volunteer, who ensured spamming and other forms of mental torture were kept to a minimum. The chat was bad enough. "Anyone in Purley?" was a high point. My suspicions about the hosts were soon confirmed. Who, after all, gives up an evening to host a chatroom?

In the interim, the world of internet dating has blossomed, but every time I dropped in on a site, such as, say, gay.com, the system of registration seemed so complex and the chat so stilted that I dismissed them all as nerdsville. Until, that was, my local branch meeting of the rosa nostra, the gay mafia. Picture the scene. I was at a friend's loft apartment in Soho (where else?), the sort of place where even the kettle has its own underlight and the various shades of grey are National Trust-approved emulsions. The men round the table were all successful, intelligent and not bad looking. OK, so my invite arrived suspiciously late in the day, but don't rub it in.

By halfway through the evening, we had long since exhausted serious conversation and things were rapidly going downhill. We had even managed to disagree on whether the lyrics of Madonna's "Ray of Light" contain coded references to the famous K-hole of ketamine -- hey, no one said this was the Symposium -- when the subject turned to boyfriends.

Jonathon, the management consultant, was torn between the German cycle courier--Wolf by name and by nature--and the blue-eyed landscape gardener. Tom, the lawyer, was fresh from wining and dining the improbably named Tristram -- I kid you not -- who was apparently a stunning model with modellish good looks. As for Paul, the curator, he was in the middle of the dating equivalent of those acts that used to grace The Generation Game: you know the ones, where they balance 200 plates at the end of wobbling sticks. All of these men were enjoying the sort of sex life I hadn't experienced since my barber and I parted company.

As they flicked through their conquests, one common factor emerged: they had all met their most recent arm-candy online. Whereas even six months ago cyberdating was thought to be little more upmarket than digital cottaging, now even the most respectable gay conversation is studded, pardon the pun, with cyberspace encounters.

One site is reaping the benefits more than any other. Gaydar, you might know, was the old camp word for the mysterious system invented by gay men to identify each other, long before shaved heads and skintight Calvin Klein T-shirts made the whole thing obsolete. The straight world had radar, gays had ultrasonic nudge and wink.

Now Gaydar, the online company, is so successful that it has launched its own internet radio station, paid for by the 4,000 men who have joined up so far. Most people begin at "classic" membership, which is free and allows only five messages to be sent or received in a day, before moving quickly to "gold", which costs [pound]40 a year and allows for unlimited messaging. The first time I signed on, there were more than 600 guys in the London room, more than 100 in Manchester and 200 in the Midlands.

The success of Gaydar is part of a trend towards making gay male cruising acceptable. Which is why the saunas and bathhouses that were regularly raided up to five years ago are now left to grow and multiply in peace, as in every other European country. The partial success of anti-HIV combinations has contributed to this new sexual openness. It helps, too, that public figures are openly gay and, even when they are not, are notably found wandering on Clapham Common, which even has its own liaison officers helping to prevent homophobic attacks. But gays are also the beneficiaries of an unparalleled era of hedonism. Straight or gay, fewer and fewer people are embarrassed to admit they seek to fulfill their sexual fantasies.

Gaydar is also testimony to the evolution of the internet itself. The older dating lines still resonate with that early internet enthusiasm, which believed that cyberspace had a duty to replace community spirit with its digital equivalent. You still enter AOL's American gay chatrooms, for example, through the improbably named "Town Hall", even if the chat is peppered with the sort of acronyms unlikely ever to enliven council amendments.

Gaydar does offer public chatrooms, but they echo with ghostly dotcom quiet. Instead, everyone signs on and joins a simple register of "Who's Online", which other members browse at their leisure. You can make a cup of tea, watch a movie, or, in the age of free internet access, leave the house and return hours later to see who has left you a message.

It could so easily be seedy. After all, people give themselves a handle which, in ten keystrokes or so, is supposed to sum them up. And admittedly, most are along the lines of SohoHung, or Ffsub4ruff (you don't want to know). But even those with the nastiest handles tend to fill out the items in their profile asking about favourite foods and actors, which is touchingly sweet.

Perhaps the main reason for Gaydar's success is that one can easily check out pictures of members. No time-consuming downloads. No opening three or four different internet explorers at the same time. You simply include a picture in your profile and you can open as many other people's pics as you like, all at the same time.

Most users of Gaydar have invested in having professional pictures taken of themselves. Some are so tasteful they are positively misleading, which means you could easily come on to someone you know by mistake -- the new nightmare dating scenario.

My journey into Gaydar has only just begun; but already it reminds me of a recent article in the New Scientist about the strange discoveries of Li-Xin Li, a physicist at Princeton University. Titter not, but he has suggested that the world might consist not of one, but twin universes, each working to slightly different laws of physics. I shall write to the professor telling him that he's on the right track -- because the world of Gaydar is almost the same as the real gay world we know and love, but there are just enough intriguing differences to suggest that it works to its own physical laws. In this twin universe, no man's penis is ever less than eight inches. Guys are shaved, not bald, and scarcely anyone admits to being passive. But one thing remains the same: when asked about their age, everyone's birthday is mysteriously five years more recent than the one their mum remembers.