Dilitazem, a coronary vasodilating agent, after oral administration of four different doses, was well and rapidly absorbed. The pharmacokinetics of the drug followed a two-compartment model, with a rapid distribution and an elimination with a half-life of 4-7 hours. After chronic treatment the pharmacokinetic parameters were practically unchanged and therefore no accumulation of the drug was observed. The comparison between capsule and tablet preparations showed that both forms had a similar bioavailability. Diltiazem was extensively metabilized and only a few percent of the drug was found in urine. Several metabolites, also present as conjugates, have been identified by means of gas chromatography-mass spectrometry.