'Whole' cauda epididymal homogenate and individual components of the cauda epididymis viz, cauda epididymal cells, epididymal plasma and sperm cells, as well as the blood plasma of the rat were screened for renin-like activity by in vivo method. Enzyme activity was high in 'whole' cauda epididymal homogenate, but very low in blood plasma. Evaluation of individual components of the epididymis revealed a relatively high enzyme activity in the epididymal cells but low activity in epididymal plasma and epididymal sperm cells. The high activity in epididymal cells was not affected by efferent duct ligation for 8 weeks and bilateral nephrectomy. Like most other epididymal functions, renin-like activity in the epididymis was androgen dependent. It was concluded that cauda epididymis of the rat contains the enzyme renin, whose activities may be predominantly intracellular.