The incidence of infection following breast reconstruction with expanders and implants ranges from 1 to 24 percent. Numerous factors associated with infection have been described; however, a one-variable at time setting and multifactorial analysis have not been performed. The purpose of this study was to analyze a set of factors that may predispose women to infection of the expander or implant. Between 1997 and 2000, a total of 168 implant reconstructions were performed in 130 women at a single institution. The mean age for all women was 48.2 years (range, 25 to 77 years). The factors that were analyzed included axillary lymph node dissection, chemotherapy, radiation therapy, tumor stage, timing of implant insertion, number of sides (unilateral versus bilateral), tobacco use, and presence or absence of diabetes mellitus. Statistical analysis was performed with stepwise logistic regression. Mean time to follow-up for all patients was 29 months (range, 12 to 47 months). Infectious complications occurred in 10 women (7.7 percent) and in 10 expanders or implants (5.9 percent). Infected implants were removed an average of 116 days following insertion (range, 14 to 333 days). Cultured bacteria included Staphylococcus aureus and Serratia marcescens. A significant association (p < 0.04) was detected between implant infection and radiation therapy. The chance for implant infection was 4.88 times greater for implants that were exposed to radiation therapy compared with those that were not. In addition, there was suggestive (p < 0.09) evidence that the chance of implant infection following lymph node dissection was 6.29 times higher than when no lymph nodes were removed. No significant association between implant infection and age, diabetes, tobacco use, tumor stage, timing of implant insertion, or chemotherapy was found.