The Aim 100

Set out on the stalls and shelves would be an astonishing assortment of products - from animal antibiotics, glues for wounds, fine wine, all manner of financial, technology and business support solutions, glamorous dresses, bags and scarves at cut-down prices to Bollywood films, juicy oranges, property deals, wealth management expertise, soft drinks and any fossil fuel or rare mineral you'd care to name.

Often young, often innovative, Aim companies are exciting, sometimes revolutionary and packed with potential and energy. Lots of them operate in the quite literally explosive world of oil and gas exploration. And although they are seen as 'growth' companies, there are a good number of dividend payers in the ranks.

But let's not get carried away. Frequently, too, Aim companies are on a one-way road to failure whether that's for lack of money or interest, poor timing, bad management or competitors with deeper pockets. And if a new Aim sector classification were to be considered, 'Dross and Walking Dead' would be as apt as any other. Illiquidity and wide spreads are additional risks.

Since its launch in 1995, more than 3,000 companies have made Aim their home - but they're not all there now, reflecting the risky nature of this market. Currently, there are fewer than 1,100 companies, with a total market capitalisation of £66bn. Around 160 have graduated to the main market, while many others have fallen into the dust by the wayside.

In just over a year's time, Aim will celebrate its 20th birthday, so what lies behind the enduring success of this market? There are at least two reasons. The first is that fast-growing companies need such a market, with its looser fitting regulations, to access funding, and the second is that there have been enough interesting companies and impressive share price gains - ASOS's 2,166 per cent gain over the past five years for example, or Judge's Scientific's near 900 per cent over the same period or even Domino's Pizza which, having spent nine years on Aim and grown its profits from a tiny £1.8m to £18.7m by 2008, then transferred to the main market – to keep investors coming back and dull the memory of the giddy rides down (WYG, Frontera Resources and African Copper, for example).

Aim shares certainly have a knack of grabbing investors' attention. But looking past the headlines to examine the companies in depth and assess their prospects as an investment can be a rather more trying experience. For a start, there's a dearth of independent analysis from the City. Yet investors need to know as much about Aim companies as they can before buying shares or making a decision to head for the exit.

There are plenty of funds that can do the job for you - see Leonora Walters's assessment of Aim funds - but whether you are investing direct or via a collective vehicle, you need to understand what Aim companies have to offer.

Now the government is planning to allow them entry into the individual savings account (Isa) tax shelter, adding to their appeal and potentially leading to a significant boost for many Aim companies.

If you don't already invest in Aim shares or you want to widen your holdings, where do you start?

Here is a good point. We write about Aim companies regularly but now, just as we do every year with our review of the FTSE 350, we've decided to publish an annual review of the 100 largest companies on Aim to help investors make an informed decision about those shares.

In this inaugural edition of the review, we focus in detail on each of Aim's top 100 companies. We look at how the company is performing, examine the investment case, give our verdict on whether the shares are worth buying and provide key financial information.

Aim 100: 100 to 51*