A randomized, double-blind crossover trial, in 10 adult healthy subjects, was carried out to compare the antibacterial and antifungal activity of a 0.1% solution of hexetidine with that of placebo. The pre-dosing oral flora of the subjects was assessed from saliva samples cultured for aerobic and anaerobic bacteria, as well as Candida albicans. Subjects then rinsed their mouths for 1 minute 3-times a day with 15 ml 0.1% hexetidine or placebo, saliva samples being collected at 2 minutes, 30 minutes, 1 hour, 3 hours and 5 hours post-dosing. Dosing was continued for 8 consecutive days on each treatment with an intervening wash-out period of 1 week. Hexetidine reduced aerobic bacterial counts on Day 1 and Day 8 by a maximum of 83% and 86%, respectively, at 2 minutes post-dosing. The reductions were statistically significantly lower than placebo up to 1 hour post-dose on Day 1 and up to 3 hours post-dose on Day 8. Similarly for anaerobic bacterial counts, 92% and 88% maximum reductions were recorded on Day 1 and Day 8, which again were significantly lower than placebo for up to 3 hours post-dose. For Candida albicans, however, the maximum reduction was 91% on the first day and 67% on Day 8, maintained for 30 minutes post-dosing. Although not eradicating completely aerobic and anaerobic bacteria, it is concluded that the substantial reduction in their numbers should prove clinically useful.