A renal blood flow (RBF) circadian rhythm and its relationship with eating and rumination was described in six once daily fed (09.00-12.00 h) caged sheep, using ultrasonic flowmeters bilaterally implanted around renal arteries. Following a rapid raise during the first 20 min after the start of feeding, the RBF progressively increased until 15.00 h (14% maximum increase, P<0.05 from 12.10 to 20.50 h compared with pre-feeding values (519 ml/min)). After 15.00 h, the RBF regularly decreased reaching its minimum values before the next feeding time. An effect of rumination on RBF circadian rhythm was not observed.