Benzyl alcohol was oxidized rapidly to electroactive benzaldehyde through a radical-chain reaction initiated by sulfate radical SO4.- electrogenerated from reduction Of S2O82-. The benzaldehyde formed was reduced via an intermediate free radical. The free radical of benzaldehyde was oxidized by both S2O82- and SO4.- 8 - to produce a catalytic wave. Based on this a novel method for the determination of benzyl alcohol was proposed. In 0.1 mol l(-1) KH2PO4 + Na2HPO4 buffer (pH 5.6 +/-0.1) + 2.0 x 10(-2) mol l(-1) K2S2O8 solution the second-order derivative peak current of the catalytic wave was linearly proportional to the benzyl alcohol concentration in the range of 9.70 x 10(-6) - 1.54 x 10(-4) mol l(-1). The limit of detection was 8.0 x 10(-6) mol l(-1). The proposed method was applied to determine the benzyl alcohol content in clinical injection.