Many drugs are both poorly water-soluble (hydrophobic) and lipophilic in nature and are therefore incorporated into surfactant micelles and monolayers. As the incorporation of drug into surfactant monolayers mirrors its distribution in surfactant micelles, the study of drug distribution into surfactant monolayers should provide useful information about the nature and extent of drug solubilisation. The present study aims to determine the amount incorporated and the extent of penetration of the hydrophobic drug testosterone enanthate into monolayers of dodecyltrimethylammonium bromide as well as the hydrophobic drugs, adrenosterone and 4-cholesten-3-one in monolayers formed by the surfactant, sodium dodecyl sulphate at the air/water surface. The study will provide invaluable information in understanding the location of the drugs in the surfactant micelles.