In a group of patients where breast reconstruction was performed at the time of mastectomy, the incidence of complications was studied. One hundred one consecutive patients had an autologous reconstruction using the transverse rectus abdominis musculocutaneous flap, and 115 consecutive patients had a prosthetic reconstruction with tissue expanders or with tissue expander and/or implant. One patient in the autologous reconstruction group had a cardiac arrhythmia requiring monitoring, but there were no other serious complications. Infection was more common in the group undergoing prosthetic reconstruction (5% compared with 3% in the autologous reconstruction group). A total of 8% of the patients in the group undergoing prosthetic reconstruction had to have their implants removed because of infection or exposure of the implant. Seven percent of the transverse rectus abdominis musculocutaneous flap patients had significant necrosis of a portion of the flap. Secondary surgical revision of the reconstructed breast was much more common (20%) in the prosthetic reconstruction group compared with 6% in the autologous reconstruction group.