The purpose of this study is to examine a cohort of patients with free-flap reconstruction prospectively and to identify the prognostic factors for postoperative medical and surgical complications. All 150 patients required a free-flap reconstruction after ablative surgery for a defect in the head and neck area. Medical complications and major surgical complications were correlated with patient factors. An ASA score of 3 and male gender were statistically significant prognostic factors for medical complications. The ASA scoring system is a slightly better prognostic factor for medical complications than Charlson comorbidity stage on forward logistic regression analysis. Female gender and an operation time exceeding 10h were statistically significant prognostic factors for major surgical complications.