AIM is an exchange regulated venue featuring an array of principles-based rules for publicly held companies.

Aside from granting leeway in regard to regulatory compliance, the Exchange also mandates continuous oversight and advice by the issuer's underwriter, referred to as a Nominated Adviser (Nomad).

Theoretically, Nomads are liable for damages from tolerating misdemeanors on behalf of their supervised companies, including the loss of reputational capital.

[4][5] AIM is an unregulated market segment, therefore it escapes most of the mandatory provisions contained in European Union directives – as implemented in the UK – and other rules applicable to companies listed in the LSE.

This may prove to be hazardous for unsophisticated investors who lack both the knowledge and resources to conduct proper inquiries into a firm's prospects and activities, or even larger investors which lack strong internal control and risk management requirements.

[2] [needs update] The following table lists the top 100 AIM companies by market capitalisation on 25 April 2020.

[7][needs update] In March 2007, U.S. securities regulator Roel Campos suggested that AIM's rules for share trading have created a market like a casino.

"[10] The comment resulted in several angry retorts, including one from the London Stock Exchange, which controls AIM, pointing out that the number of companies that go into liquidation or administration in a year is actually fewer than 2%.

[20][21] In March 2007 The Daily Telegraph noticed a tendency to use listing vehicles incorporated in offshore financial centres prior to floating on AIM.