The pharmacokinetic properties of a single oral dose of 100 mg of tiapride were studied in six patients with Huntington's disease. The results for five patients were consistent with a two compartment open model. Peak plasma concentrations were observed within 2 h following drug administration with a mean value of 0.92 micrograms/ml being recorded. The drug was rapidly eliminated as unmetabolised tiapride in the urine, 51% of the dose was recovered in 24 h. The plasma elimination half-life was 5.3 h and the average apparent plasma clearance was 16.6 l/h.