Recovery of hepatic function following orthotopic liver transplantation includes the ability to produce 'adequate' bile. What constitutes adequate bile flow, however, has not previously been defined. The present study was undertaken to characterize biliary water and electrolyte secretion following hepatic transplantation. Bile was sampled from nine liver transplant recipients for 15-25 consecutive days during chronic t-tube biliary drainage. Liver biopsies and t-tube cholangiograms were unremarkable in all patients. During the first post-operative day mean bile flow, bile salt concentration, [BS], and bile salt output (BSO) were 60.0 microliters/min, 6.8 mM and 0.41 mumol/min, respectively. [BS] increased over days 1-5 and then plateaued at 12.2 mM over days 6-25 post-transplant. BSO and bile flow increased over days 1-12 before achieving steady-state values of 4.52 mumol/min and 334.7 microliters/min, respectively. In each patient bile flow increased linearly with increasing BSO. Choleretic index (CI), varied from 36.9-77.1 microliters/mumol (mean: 50.7 +/- 8.8). The y-intercept for this relationship ranged from 52.4-156.9 microliters/min (mean: 95.9 +/- 81.8). Only primary bile salts (82% cholate and 17% chenodeoxycholate), were observed in the bile of each patient. Biliary electrolyte concentrations were similar to that observed in plasma. Each was relatively unaffected by changes in bile flow and BSO. Electrolyte outputs increased linearly with respect to both BSO and bile flow. We conclude that recovery of bile secretion following orthotopic liver transplantation occurs gradually over a 10-12 day period and is strongly dependent upon bile salt secretion.