Many surgeons apply povidone-iodine (PVP-I) to the skin around an incision before closing a wound to reduce wound infection rates. However, the effectiveness of this procedure has not been proven. Forty-seven cases of gastric surgery and 60 cases of colorectal surgery performed at Kanto Medical Center between July 2004 and December 2004 were randomly assigned to the group with PVP-I or the group without PVP-I. Wound infection and surgical site infection (SSI) rates were compared between these two groups. Applying PVP-I was effective in eliminating skin contamination, as cultures became negative in all cases after applying PVP-I. However, this study could not demonstrate the reduction of wound infection or SSI in the group with PVP-I, possibly because the number of cases in this study was too small to make a difference. Subcutaneous tissue contamination was considered a more important factor than skin contamination in causing wound infection.