The transport behavior of steroid hormones and their derivatives was investigated in a liquid membrane system with bovine serum albumin (BSA) as a carrier separating a hexane source phase (I) and a hexane receiving phase (II). The rate constant of hormone uptake from the hexane phase (I) to the water phase was designated as k₁ and the rate constant of release from the water phase to the hexane phase (II) as k₂. Positive correlations were found between k₁ and the water/hexane partition coefficient of the hormone, while inverse correlations were noted between k₂ and the partition coefficient with and without added BSA. For lower partition coefficients, hormone uptake from the hexane phase (I) was rate-determining in the transport process, while release of the hormone from the water became so with increase in the partition coefficient. Transport behavior through the water membrane was governed primarily by partition coeffcients between the water/hexane phases. For hormones, whose partition coefficients were less than 0.02, transport was accelerated by the addition of BSA. For hormones with partition coefficients over 0.02, the rate of transport lessened on addition of BSA.