Recently, reverse micellar systems and microemulsions play an important role in special enzyme reactions. Amongst the possible systems suited to enzymic applications the aggregates formed by AOT in isooctane-water solution appear to be favoured. This work presents a critical review of the structure and properties of the AOT/isooctane/water system including formation of micelles, critical micellar concentration, size of micelles, solubilization of water into the polar core of the micelles, the connection of the size of aggregates with the water content, the phenomenon of transition from micellar phase into microemulsion and the effect of temperature on the system.