Based on pharmacokinetic data from mice, rats, and rabbits, the prediction of pharmacokinetics of intravenous metazosin in man has been performed. The correlations were based upon allometric scaling of plasma clearance and the volume of distribution at steady-state. A one-compartment body model approximating clinical pharmacokinetics fits well the elimination phase of subsequently measured metazosin concentrations in volunteers. Fitting human pharmacokinetic data to allometric equations enabled us to superimpose pharmacokinetic curves from different species.