Extrinsic discoloration of teeth has frequently been observed in connection with the use of chemical plaque-preventive agents. Preliminary investigations have indicated that oxidizing peroxymonosulfate may effectively reduce this discoloration without interfering with the plaque-preventive capacity of chlorhexidine. In the present experiment a 0.2% chlorhexidine and a 1% peroxymonosulfate solution were used for oral rinsing in a group of 50 military recruits. A double-blind experimental design was followed. The plaque-preventive capacity of chlorhexidine was maintained, and a marked reduction in extrinsic tooth discoloration could be observed.