The melanosome fraction of Xenopus laevis oocytes was found to bind progesterone specifically. The binding is of high affinity and low capacity and displays a mean dissociation constant K_d = 5.8 ± 3.2 × 10⁻⁸M at 4°C. Preliminary characterization of the receptor was performed and experiments attempting to assign a biological role in relation to oocyte maturation are discussed.