Eight healthy volunteers were given single i.v. and oral doses of clonazepam (2 mg). The disposition curves after i.v. administration showed a biexponential decline and the data were applied to a two-compartment open model. The volume of distribution ((V_d)) ranged between 1.5 and 4.4 l/kg and the plasma half-life (t_1/2) between 19 and 60 hours. Absorption after oral administration was fast, with peak plasma concentrations within 4 hours in all subjects. Five of the subjects received repeated oral doses of clonazepam 0.5 mg bid for 15 days. The plasma level during steady state (estimated as C_min within the dose interval) could be predicted from the constants A, B, and obtained in the single dose study with a coefficient of variation of 6%. The plasma half-lives after cessation of the subchronic dosing were of the same magnitude as after single doses.