A simple method of estimating the extent of biliary recycling using blood level and cumulative biliary excretion data from control and bile duct-cannulated animals is described. The method was tested in rats following an intravenous dose of [14C] temazepam. It was shown that 62% of the drug excreted in the bile of control rats was reabsorbed during each enterohepatic cycle, contributing to the secondary peak blood concentrations and a prolonged elimination half-life.