Abstract Objective: To investigate an outbreak of surgical site infections (SSI) in a vascular surgery unit. Setting: A 60-bed unit of vascular surgery, where surgeons performed an average of 30 operations per month at the Hospital do Servidor Público Estadual, a 1,000-bed tertiary care hospital in São Paulo, Brazil. Design: We included in the case group nine patients who had limb amputations or arterial reconstructions, October 16 through 23, 1992. We included in the control group patients whose operations were performed within 30 days of the outbreak period. Control patients were matched for sex and type of operation. Results: Six of 9 case patients experienced SSI, as compared with 3 of 18 control patients ( P = .026) and 28 of 244 patients in the pre-epidemic period ( P = .0002). Risk factors were identical for case and control groups. Factors assessed were American Society of Anesthesiology (ASA) status, duration of surgery, wound class, emergency status, remote site infections, preoperative length of stay, use of prophylactic antibiotics, and underlying diseases. Possible common sources also were analyzed. No differences were observed concerning hair removal, preoperative shower, wound dressing, and surgical team present in the operating room. During the outbreak period, the operating room was not provided with povidone-iodine, used in our hospital for skin cleansing and handscrubbing. Surgeons from all departments, including vascular surgery, used 2% iodine with 70% alcohol for skin cleansing. Surgeons from other departments used this iodine solution for handscrubbing, but the vascular surgeons used plain soap for handscrubbing. No increases in SSI rates were reported in other services. Comparison of case and control groups for handscrubbing was statistically significant (P<.00001). After reinstitution of povidone-iodine, only one SSI was diagnosed in 13 vascular procedures. Conclusions: Although we could not demonstrate definitely that scrubbing with plain soap was related to SSI, we found a strong suggestion of this association