Interest in microbially produced biosurfactants has increased recently, due mainly to their potential as agents in enhanced oil recovery. A variety of microbes and their products have been assessed for their surface-active properties, and it has been suggested that biosurfactants may prove useful in a broad spectrum of potential applications which presently utilise synthetic surfactants. The most commonly produced biosurfactants tend to be glycolipids, usually a mono- or di-saccharide attached to a fatty acid, but more complex molecules such as lipopeptides, lipoproteins, and lipo-heteropoly-saccharides have been isolated and studied. Biosurfactant production by microbes is often but not invariably enhanced by the addition of hydrocarbon to the growth medium, and needs to be optimised by controlling such factors as carbon source, nitrogen source and concentrations, aeration and metal ions. Biosurfactants have been shown to be as effective, if not more so, than many conventional synthetic surfactants and their future utilisation may depend utilimately upon the prevailing economics for their production.