The anti-pruritic effects of rifampicin (10 mg/kg) and phenobarbitone (3 mg/kg) were assessed in 22 patients with primary biliary cirrhosis in a crossover randomised clinical trial. Each agent was given for 14 days, with a 30-day washout period between treatments. 21 patients completed the course of rifampicin and 18 that of phenobarbitone; rifampicin was withdrawn from 1 patient when anaemia and renal failure developed, whereas 3 patients stopped taking phenobarbitone because of a rash and the 4th merely refused the drug. Rifampicin had a greater anti-pruritic effect than phenobarbitone. The symptom improved in 19 patients taking rifampicin and in 8 taking phenobarbitone, the degree of improvement being greater with rifampicin than with phenobarbitone. Pruritus disappeared in 9 patients receiving rifampicin, and three of them were free of itch when switching over to phenobarbitone. Both drugs were equally effective in inducing hepatic microsomal function but rifampicin has the additional effect of reducing cholestasis. Its anti-pruritic effect should be tested in long-term clinical trials.