Immediate reconstruction of a breast removed for treatment of carcinoma can be accomplished without altering the cancer-ablative surgical procedure. The theoretical possibility that reconstruction might compromise the cure rate has tempered enthusiasm for this approach. To test this issue, the relapse-free survival of 101 patients who underwent breast reconstruction in the immediate postmastectomy period was compared with that of 377 patients with breast cancer who underwent mastectomy without immediate reconstruction. This comparison was accomplished using multivariable statistical techniques to correct for baseline inequalities between the patient groups. After adjustment for the relevant prognostic factors, no significant difference remained between the two groups. We conclude that immediate reconstruction has no discernible adverse influence on the natural history of surgically treated breast carcinoma.