This study investigated the factors influencing the effectiveness of 7.5% polyvidone iodine as a surgical antiseptic. The study involved 100 operating staff (75 doctors and 25 nurses) from hospital surgical teams. Fingertips of both hands of the subjects were pressed on to agar culture before and after washing and after completion of surgery. Handwashing tasting for more than 3 min led to a significant decrease in the number of colonies compared with handwashing tasting for less than 3 min. Moreover, the number of colonies was significantly higher when surgery lasted for longer than 95 min. However, the handwashing style (with or without brushing) was not found to have a significant effect on the outcome of the disinfection procedure in terms of bacterial, colonization. Subjects who had colonization of their hands after surgery were found to have significantly higher colony counts before handwashing compared with those who did not have any colonization on their hands after surgery. The results of this study revealed that in order to attain effective disinfection with potyvidone iodine, the duration of handwashing should be at [east 3 min. The risk of recolonization increases when the duration of surgery exceeds 95 min. (c) 2005 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.