Next weekend marks the 20th anniversary of the Mind Body Spirit Festival, an annual gathering of everybody and everything "alternative". The first festival was held in 1977 and attracted a few thousand hippy-types. Strangely, the festival survived the materialistic Eighties and is now larger that ever. From Friday 18 May, not-so-New Agers will gather in their thousands.

how did it start?

The festival is the brainchild of a businessman called Graham Wilson, who is now its director. In the early days, he put up with press derision (they quickly dubbed the festival the "homely ideals exhibition") to give space to an incongruous collection of exhibitors - from alternative medicine practitioners and animal welfare groups to sellers of pyramids that you could place over your houseplants to speed their growth. As punk took the nation by storm in the late 1970s, the festival became a refuge for flare-wearing hippies - where else could they learn the finer points of macrobiotic cookery and buy "only rotters hunt otters" badges?

have all the flowers gone?

Not quite. It is true that many of the ideas from those early gatherings have entered the mainstream, together with many early exhibitors (shops like like the Body Shop and Holland and Barrett); it is true, too, that the festival has a more businesslike image these days, with tie-dye backdrops and scrawled information sheets being replaced by neat display stands and glossy brochures. But some things never change - the whole festival is still a no-smoking zone, and catering remains strictly vegetarian.

what's there?

Around 200 exhibitors, workshops and lectures covering subjects from auras to yoga with some strange concepts in between. One of this year's big attractions is the Kirlian photography demonstration which claims to capture an image of your body's energy field by taking an imprint of your hand. From this, say its exponents, it is possible to spot serious health deficiencies. Then there's the BioElectric Shield stand which sells small discs that the makers promise offer protection from the negative effects of computers, cell phones and, for some reason, hairdryers. "Users report balanced energy, increased vitality and concentration, clearer thinking, lower stress," promises the blurb. But the hottest topic at the festival looks set to be feng shui, the Chinese belief that aligning living and working spaces in a particular way can encourage well-being and prosperity.

are there any star turns?

There certainly are. Some of the big names in alternative thought will give talks and run workshops that, depending on your point of view, are signposts to enlightenment or implausible nonsense. On Saturday the American author Denise Linn will deliver a lecture called "Angels! Angels! Angels!" in which she will reveal how to recognise your personal guiding spirit and call it into your life. The following day the Canadian Indian medicine man Tim Sikyea, the African shaman Percy Konquobe and the German druid Andrea von Schnoy will lead a session on how to "let go of man-made illusions" and "lighten your energy" through traditional rituals. Other attractions include a demonstration to show how yoga can reduce cellulite, and the chance to celebrate life through belly dancing.

how about audience participation?

This is not a place to come along and gawp. On Saturday afternoon the whole exhibition will take part in a mass healing session led by Matthew Manning, presenter of the television programme Beyond Belief. Every stall will cease trading and you will become part of a hand-holding circle of 5,000 people. The gathering will "generate a surge of healing energy to be projected to those in need", which will have physical, mental and spiritual benefits. Don't worry if you can't be there in person though - the organisers promise that anyone in need of healing can "tune in" at just after 2.35pm from wherever they are.

isn't a load of old hokum?

That, I'm afraid, is up to you to decide.

how do i get there?

The Mind Body Spirit Festival is at the Royal Horticultural Halls, Greycoat Street, London SW1, and runs from Saturday 18 May to Monday 27 May; admission is pounds 6 for adults, pounds 3 concessions and pounds 2 children. Opening times are from 10.30am to 7.30pm at weekends, and 11.30am-6pm Monday to Thursday. For more information call 0171 938 3788.