A specific, sensitive and reproducible high-performance liquid chromatographic procedure was developed for the quantitative analysis of carboplatin in human plasma. Plasma was ultrafiltered with an Amicon Centrifree system and then injected onto an analytical NH2 column. Carboplatin was monitored at 230 nm and eluted by 10 min using acetonitrile/methanol/5 mM sodium perchlorate buffer (pH 2.4) (75:15:10, v/v) as a mobile phase. The method yielded intra-day and inter-day precision and accuracy of <6% with a linearly from 0.1 to 80 microg/mL and a recovery of >98%. Plasma concentrations of intravenously administered carboplatin in three patients could be determined by this system. Slightly higher plasma concentrations of carboplatin were detected even 30 min after hyperbaric oxygenation therapy for 60 min than expected. The results suggest that this method could be applicable for measurement of carboplatin in plasma samples to evaluate carboplatin therapy together with hyperbaric oxygenation.