Intraluminal pressures in the seminiferous tubules and in various regions along the epididymis of the rat were measured by micropuncture using a servo-nulling pressure transducer system. The intraluminal hydrostatic pressure in the testis was significantly lower than that in all regions of the epididymis. There was an increasing pressure gradient from the caput to the cauda epididymidis. Spontaneous contractions were observed in all parts of the epididymis but not in the seminiferous tubules. The amplitude of contraction in the epididymis increased from the caput to the proximal cauda. However, an appreciable decrease in the amplitude occurred in the distal cauda, although the frequency of contraction declined from the proximal caput to the distal cauda with substantial reductions in the mid-caput and the proximal cauda.