The concentrations of cytoplasmic receptor sites for androgens in the caput, corpus and cauda epididymidis and the effect of ligation of the efferent ducts and testosterone treatment after bilateral castration on the concentration of receptors in the caput were measured. Androgen receptors in the ventral prostate were measured in the same animals for comparison. The caput had the highest concentration of receptor sites, the corpus the lowest. The ligation of the efferent ducts had no effect on this concentration which is dependent on testicular androgens. The present data do not yet allow explanation of the differential response of the different regions of the epididymis and of the other accessory glands to the administration of androgens.