Microbial infections reportedly have a favorable effect on the course of certain malignant diseases. Intralesional inoculation of micro-organisms can bring about tumor regression in certain clinical and experimental situations. In order to evaluate the influence of immediate postoperative wound infection on the course of Stage II melanomas, a retrospective study was undertaken of 211 patients who had undergone axillary or groin dissection. None had any antibiotic, steroid, chemoimmunotherapy, or cryosurgery and there was no history of a second primary neoplasm, pregnancy, immunodeficiency, or administration of immunosuppressive drugs. Forty of these patients developed significant postoperative wound infections. Although their representation according to sex, tumor location, number of nodes involved, and other parameters was comparable to that of the remaining 171 patients who did not develop wound infections, the incidence of local recurrence in the group with infections was significantly lower (p less than 0.01). Patient survival and disease-free interval following node dissection were not influenced by infection. Postoperative infections in the groin or axilla offered only local protection from tumor recurrence; the ultimate course of the disease was not affected.