To most men, what Damian Callinan is doing would be beyond the pale. Under the unrelenting glare of spotlights, the Australian stand-up comedian is relating his experience of infertility to a room full of strangers and holding up a peach-coloured pebble to illustrate the exact nature of his problem.

In his homeland, the show, a monologue set in a sperm delivery clinic, proved particularly potent as it was the first time he had strayed into biographical territory. While virtually unknown here, his career in Australia includes a long list of television and radio shows and he has twice been nominated for the Barry award (named after Barry Humphries), the most prestigious award at the Melbourne Comedy Festival. He is now in Edinburgh to perform to an international audience.

A former teacher of drama and English at a Catholic secondary school, Damian, 43, says he has always had a desire to perform. As a six-year-old child, his party piece was dropping his pants to reveal surgical scars on his testicles. This eyebrow-raising turn was always accompanied by the mantra: "If I hadn't had this operation I wouldn't be able to have babies when I get married."

Following in the established stand-up tradition of mining real-life horror for comedy nuggets, Damian has had rich pickings. "Norm the baker came to the door and I was telling him about the operation and he says, "Well go then, show us". I remember not batting an eyelid and just dropping my pyjamas and him flipping me a 20 cent coin." Re-telling the story, he breaks into a laugh and concedes that perhaps Norm was a little strange. "Yeah, Norm left soon after."

Damian's condition first came to light when the district nurses came to his school to carry out the dreaded health check. Aged six he was diagnosed with cryptorchidism, or undescended testes, and told that surgical intervention was required to make them descend into the scrotum. The procedure was successful and left Damian with some impressive scars, and a desire to have children. "I remember knowing that I wanted to have babies," he says.

After the operation, he and his family believed that the problem had been rectified and promptly forgot about it. It wasn't until he was 31 that Damian discovered that he was infertile. Four months later, his seven-year marriage was over.

He had met his wife, a fellow teacher, when he was 21 and they married when he was 25. He describes the infertility bombshell as the catalyst for the split but not the cause. "I probably shouldn't have got married in the first place but one bad decision leads to another," he says. "She was desperate to have kids."

His infertility came to light after several years trying to conceive. "The investigations started with her but they said they'd test me while they were waiting for her results. Those results completely took me by surprise. I'd had a massive period in my life where I'd just assumed that everything would be alright," he says.

With hindsight, he admits that the signs had been there. The fact that his earlier cavalier attitude to contraception had never resulted in pregnancy came back to haunt him.

His wife's negative reaction to the news provided the death knell for the marriage. He ended the relationship but describes it as the hardest thing he has done. "Soon after we broke up, she had a fling and got pregnant and has a kid." He insists, though, that he was not bitter then and is not now. While he is disarmingly frank about his own physiology, he finds it far more difficult to talk about his marriage and its demise.

"I would have preferred not to talk about it at all because it's someone else's story, but it's such a cornerstone of the story, because the end of the marriage was the reason why I didn't address what was wrong for such a long period of time. It is an incredibly difficult thing to talk about."

At one gig, a farmer and his wife rendered him speechless. "I had a weird chat with him and then his wife, in classic country town you can't have a lull in the conversation' thinking, asked: So Damian, have you got any kids?'. Er, you've just watched my show for an hour. No, I don't.'"

For the most part, though, audience reaction has been more different to that of his other shows, in a good way. "They were a bit more caring. You could see the smiles on their faces, not patronising but just transfixed because you've let them into something," he says. Although well-known in Australia, Damian admits that being a new face in Edinburgh may have tempered the reaction somewhat. "There have been a couple of nights here where, because there is no previous connection, particularly with the men, it's a little bit more reserved."

Although he was initially more interested in charting his own story as opposed to being a pioneer of men's health issues, doing research for the show made him think differently. "I could find virtually nothing written about male infertility and what there was, was written by women. Around 45% of infertility is male and yet less than 1% of literature is about it.

"Women would e-mail saying that their partner or husband had loved it and felt a lot better having seen it, and for me, that almost vindicates the show."

It was only while he was researching the show that he delved back into his own condition, cryptorchidism. He discovered that almost 40% of boys who undergo the operation which he did, called a bilateral orchidopexy, will later discover that they are infertile. They also have a much higher chance of developing testicular cancer in their forties.

After more than a decade of believing that he had no chance of becoming a father, he had come to terms with his infertility. "Over a period of time, children have been a massive part of my life. I taught for 12 years, I looked after state ward kids, I've done children's shows, so there is obviously a natural connection between me and children. I've come out of it though thinking, that doesn't necessarily mean that I'm ordained to have children. That connection with them can just be as it is."

However, on revisiting his file, a doctor told him that he could undergo an exploratory operation to extract any trace of sperm, although the chance of it leading to fatherhood was very slim. "I really don't want to have the operation," he says. "It's such a lot to put yourself through for probably no result. For years I thought I couldn't have kids and was completely comfortable with it and so this tantalising news was a little bit disconcerting because it was actually chipping away at who I had moulded myself into. Having said that, I've also got to a point where I'd be happy to change my mind, depending on who I'm with."