AbstractThe voltammetric reduction behavior of ozone in an acidic solution was examined at gold, platinum, glassy carbon, and graphite reinforcement carbon (GRC) electrodes. The GRC electrode, the lead of a mechanical pencil, exhibited a well‐defined ozone reduction wave at 0.8–0.9 V versus a saturated calomel electrode (SCE) on a flat base current, whereas gold and glassy carbon electrodes were insensitive or nonselective to ozone. The platinum electrode showed no base current and, hence, made background correction difficult. The response was not degraded by long exposures of the GRC electrode to the ozonized solution. The reduction of ozone at the GRC electrode was controlled by a sluggish charge‐transfer step and diffusion. Differential pulse voltammetric peak current showed a linear variation with ozone concentration up to the detection limit of 6 × 10−7mol/dm3ozone in acidic solutions. Residual ozone in tap water disinfected by chlorine was determined by the present method; a linear calibration curve was also