A flow-injection method is proposed for the determination of chlorpromazine and other N-substituted phenothiazines. The procedure is based on the oxidation of analyte with lead dioxide entrapped into polymeric material in a packed-bed reactor. The oxidation of the drug yields soluble Pb2-, which is monitored by means of the lead ion selective electrode in the wall-jet configuration. The calibration graph is linear over the range of 0.01 – 2 μg ml−1of chlorpromazine with relative standard deviation of 1.4% and sample throughput 20 h−1. The developed method was applied to the determination of chlorpromazine in pharmaceutical preparations.