SUMMARY: Cyclical changes in the activity of adrenocortical tissue are a wellestablished phenomenon in many amphibian species but up to now they have been studied by observing changes in cytology or enzyme activity, e.g. steroid-3β-ol dehydrogenase. The present study was designed to provide a measure of corticosteroid secretion throughout the seasons using the in-vitro approach. Concomitant histological changes are also recorded and together provide evidence that the adrenal tissue of Rana rugulosa shows maximum activity in the spring spawning season and reaches a minimum in winter.