['To determine whether external beam radiation therapy (XRT), administered either before or after surgery, increases the rate and/or severity of local postoperative complications in patients with head and neck cancer who undergo microvascular free flap reconstruction.', 'Retrospective cohort study.', 'University of Washington Medical Center, Seattle, a tertiary care hospital.', 'A total of 100 consecutive patients underwent fibular free flap reconstruction of the mandible. The study cohort was divided according to radiation treatment status: (1) no XRT (28 patients), (2) preoperative XRT (37 patients), and (3) postoperative XRT (35 patients). The median follow-up after surgery was 11 months (range, 1-89 months).', 'Rate and severity of local postoperative complications.', 'Fifty-four patients (54%) had at least 1 postoperative complication. There were no differences among the 3 XRT subgroups in the overall proportion of patients with complications of any severity (15 [54%] of 28 patients in the no XRT group, 24 [65%] of 37 patients in the preoperative XRT group, and 16 [46%] of 35 patients in the postoperative XRT group; P = .26, chi(2) analysis). There were also no differences seen when mild and severe complication rates were specifically examined (P = .58 and P = .10, respectively). No case of complete flap loss was observed. We noted no significant correlations between the rate of postoperative complications and the following covariates: total radiation dose, size of radiation field, disease stage, exposure to chemotherapy, presence of serious medical comorbidities, patient age, or history of tobacco use.'] Does radiation therapy impact local complication rates after free flap reconstruction for head and neck cancer?