To elucidate the pathogenesis of renal insufficiency associated with obstructive jaundice we have studied spontaneous water intake and body water compartments in rabbits undergoing common bile duct ligation. Total body water, extracellular water and plasma volume were measured by multi-isotope dilution technique. During the initial 6 postoperative days spontaneous water intake was 898 ml in sham operated animals (SO) but only 280 ml in jaundiced rabbits (OJ6) (P less than 0.01). Creatinine clearance was almost unchanged in SO but fell to 60 per cent of the preoperative values both in OJ6 and in paired-drink sham operated animals (SO2). There was a 15 per cent decrease in total body water (P less than 0.01) and a 24 per cent decrease in extracellular water (P less than 0.01) 6 days after bile duct ligation. There was a further reduction of the extracellular water to 35 per cent and a 15 per cent reduction of plasma volume 12 days after ligation. Water restriction mimicked the alterations in body composition produced by bile duct ligation. We conclude that bile duct ligation is associated with hypodypsia and a depletion of extracellular water and plasma volume. These alterations could explain the tendency to develop hypotension and renal failure which are associated with obstructive jaundice.