The antimicrobial potency of 4 per cent chlorhexidine gluconate was compared with that of 10 per cent povidone-iodine (1 per cent free iodine) on the vaginal bacteria of 150 premenopausal, non-pregnant women. From 30 of the women blood samples were taken before and at either 15, 30 or 60 minutes after vaginal cleansing with chlorhexidine for chlorhexidine analysis. Five minutes after applying either chlorhexidine or povidone-iodine almost 99 per cent of bacteria present on the lateral wall of the vagina were killed. Chlorhexidine was significantly more effective than povidone-iodine. Serosanguineous , mucoid or white-yellowish vaginal discharge did not alter the effectiveness of either antimicrobial agent. In contrast to povidone-iodine, vaginally applied chlorhexidine was not absorbed in measurable amounts (sensitivity of detection method: 0 X 1 mg/l) into the bloodstream. Chlorhexidine may therefore prove of value for treating vaginitis especially during pregnancy and also for combating microbes such as Group B streptococci which are potentially harmful to the newly-born child.