The use of butyl lactate as cosurfactant on the preparation of microemulsions with anionic surfactant is suggested. A parallel study between the classical system water/sodium dodecyl sulphate/pentanol and the proposed water/sodium dodecyl sulphate/butyl lactate has been carried out on their capacities of incorporating heptane as lipophilic component. The results obtained show the ability of butyl lactate to prepare microemulsions, allowing the incorporation of heptane up to contents of 30–40% at higher dilutions with water than the classical system containing pentanol.