Ten students walk into a pub...

...is this a joke? asks Michael North as he sits through gratuitous obscenities and some charming wit in a performance that's part of a stand-up comedy course.

The atmosphere in the Laughing Horse comedy club is thick with smoke and perspiration. Crammed into the scruffy upstairs room of the Britannia pub in Richmond upon Thames are what seems like a hundred or so excited students and a handful of older, more distinguished patrons like me.

They are here for a second night of comedy delivered by students who signed up to the stand-up comedy module offered by Roehampton University's English department.

The quality of the comedy is, to be brutally honest, variable: it ranges from the offensive and totally unfunny to the charmingly disarming. Into the first category falls Chris, a ginger-haired lad whose idea of comedy seems to be to offend as many people as he can - his five minutes in the limelight include a joke about baby rape, paedophiles and obscenities fired at every target from Tony Blair to Sharon Osbourne and the X Factor judging panel.

Other less than successful performances come from Dennis, who is so consumed by giggles that the only thing I can make out is the line "marriage is shit"; and James, whose adrenalin-fuelled performance is marred by hysterical swearing for the benefit of friends and his dad in the crowd.

He is one of the lads who try too hard to amuse, or who remind me just a little too much of Ricky Gervais.

The most successful acts are, surprisingly, the least confident in their power to be funny, and as a result you can hear jokes that are all the better for being understated and, mostly, clean. These performers are all female. There is well-spoken Kerry, who has a funny line about her nan's hypochondria: "It's the only illness she won't admit to." There is Trisha, a generously proportioned streetwise black Londoner who makes fun of her "24-hour-glass figure". And there is pocket-sized Sarah, who focuses her whole act on the fact that she is vertically challenged. She laments the fact that short people have to sit in the front row of school photos "with their hands folded like a pansy" because they can't stand at the back, and she jokes about small-size ladies' clothes being labelled "petite" to "soften the blow". "At least I don't qualify for the hobbit range," she says. Hers are endearing rather than startlingly funny lines, and the audience likes her. I am reminded of something Kevin McCarron, the tutor of the stand-up course, told his class when I observed him a few weeks earlier: "Woody Allen said the biggest mistake is to think that everything depends on the material. A great attitude is the most important thing. If the audience likes you, you don't need great material."

McCarron is not your average academic. For a start, he looks quite scary - he smokes roll-ups, is bald and has a sharp delivery that implies "I take no nonsense", which he uses to hush noisy youths as he comperes the comedy night.

McCarron, who was born in New Zealand, left school with few qualifications and came to Britain to work as a roadie for rock bands. It was while shifting scenery at the Lyric Theatre in Hammersmith that he decided to go to university. "I spent hours reading in the theatre's green room," he says. He eventually read for his PhD in English literature at Queen Mary and Westfield.

But McCarron, who is 54, always kept a foot in the performing arts: he has been involved in stand-up comedy since 1979 and now runs the Laughing Horse club in London, and other acts outside London, and has 1,500 comedians on his books. "After watching so many comedians, I thought certain aspects of this can be taught," he says.

His stand-up comedy module at Roehampton is growing in popularity. There are now 35 students taking a course that lasts a 12-week semester and covers the history, theory and performance of stand-up. Texts studied include Tony Allen's Attitude: The Secret of Stand-Up Comedy , Oliver Double's Stand-up: On Being a Comedian and John Osbourne's The Entertainer .

"Stand-up started with the role of the jester to entertain the king and to remind him that he was human," McCarron says. "Today it is the comic's job to take the piss out of President Bush."

Students have the option of writing and performing a five-minute routine for 50 per cent of their course marks, or they can write a third essay. The stand-up routine is marked on its originality and tightness rather than the confidence of the performer.

McCarron has enlisted the help of a professional comedian, Jay Sodagar, to teach the stand-up workshops. I join him for a class in which he critiques students' routines. He tells them not to be afraid to edit out the meandering digressions that dilute punchlines, to put more of themselves into their routines, and he imparts pearls of wisdom from his time on the circuit. After one student's constant punning on the theme of shopping - "Why don't Harrods sell amusing fishing rods?" - Sodagar warns of the dangers of using puns, especially those that have been heard before: "If you use other people's gags, comedy bookers may not use you again."

There is real talent on display in the class of 14 male and three female students. Most striking are Leon, "the black Ronald McDonald", and sardonic Dillon, with his acerbic attack on Christianity. "So God is this big, jealous man with a beard who gives us temptation. It's as logical as having a stereo and giving it a kicking because it won't make toast," he says. The class is fun and there are a lot of laughs.

After the session, Bernie Mitchell, a postgraduate student, describes what last year's stand-up module gave him. "Doing the course really impacted on my MA study in religion and literature because of the clarity you have to have to get an act to work. It's like going to a gym for the mind," he says.