The cancer chemotherapeutic cis-dichlorodiammineplatinum (cis-DDP) was administered to 8 patients (1-hr intravenous infusion) at a dose of 70 mg/m2. Plasma and urine concentrations of platinum were determined by flameless atomic absorption spectrometry. Measured plasma platinum concentrations revealed a biphasic clearance of platinum with half-life values of 23 min and 67 hr. Platinum values obtained 3 wk after the infusion indicated that a third excretory phase might be present. Urinary measurements showed 17 +/- 2.7% of the administered dose excreted in the first 4 hr and 23 +/- 3.9% excreted in the first 24 hr. Renal excretion appears to be predominantly by glomerular filtration. Non-protein-bound plasma platinum values were calculated and the non-protein-bound platinum was found to be rapidly and biphasically cleared from the plasma with half-life values of 8 to 10 min and 40 to 45 min.