The pharmacokinetics of sulpiride was studied in 6 healthy volunteers after intravenous and oral (tablets) administration of 100 mg. An open two- and in two subjects a three-compartment model was applied following intravenous administration. The average total distribution volume during the terminal slope was 2.72 +/- 0.66 l/kg and total systemic clearance was 415 +/- 84 ml/min. The serum half-life of the terminal slope following intravenous administration averaged 5.3 h (range 3.7--7.1 h) according to the two-compartment model. In two subjects the half-lives were 11.0 and 13.9 h when the three-compartment model was applied. Determinations of urinary excretion rates of unchanged sulpiride indicated a half-life of 7.15 h. Following intravenous administration, 70 +/- 9% of the dose was recovered unchanged in urine within 36 h; the mean renal clearance was 310 +/- 91 ml/min. Sulpiride was absorbed slowly, with peak concentrations appearing between 3 and 6 h after oral administration. The recovery of unchanged drug in urine following oral administration was 15 +/- 5% of the dose, with a mean renal clearance of 223 +/- 47 ml/min. The bioavailability determined from combined plasma and urine data was only 27 +/- 9%. The low bioavailability was probably due to incomplete absorption.