Forty-four patients were reviewed to determine the incidence of atelectasis following pectoralis major myocutaneous flap reconstruction of head and neck defects. Patients underwent tumor resection with subsequent pectoralis major myocutaneous flap reconstruction (flap group, n = 24) or another major head and neck procedure (control group, n = 20). Chest roentgenograms taken on the first postoperative day were scored for atelectasis by preestablished criteria. Sixty-five percent of control and 70% of flap patients demonstrated postoperative atelectasis roentgenographically. The flap patients with skin paddles larger than 40 cm2 had a 60% incidence of major atelectasis compared with 5% in control patients. The skin island area was strongly correlated with the atelectasis score in the flap group. These results suggest that atelectasis is common following pectoralis major myocutaneous flap reconstruction of head and neck defects. As well, decreased chest wall compliance after primary closure of large donor defects may contribute to the atelectasis observed.