Ojectives:Considerable controversy exists over optimal intra and peri-operative fluid management for patients undergoing complex reconstructions of the head and neck with free tissue transfer. The purpose of this study was to determine whether peri-operative fluid management or any other patient or treatment related factors predicted peri-operative surgical and medical complications. Materials and Methods: 185 patients undergoing free tissue transfer to a head and neck site between January 1999 and January 2001 were evaluated retrospectively. A comprehensive group of patient and treatment related parameters were collected including indices of co-morbidity, fluid management by type, volume, and duration, drugs, including antibiotics and anesthetic agents. Outcome measures included operative time, LOS, surgical complications, medical complications and flap loss.Statistical analysis included univariate and mulivariate regression of treatment and patient variables. Results: 185 patients suffered 18% major surgical complications and 30% major medical complications. There were 10 patients who underwent re-exploration of their flaps with 6 salvaged. Using univariate analysis predictors of medical and surgical complications included only ASA class and Kaplan-Feinstein co-morbidity index. Volume of fluid, colloid or crystalloid and intraoperative anesthetic agents were not correlated with medical or surgical complications. Conclusions: Based on this retrospective review of 185 patients, the single most important predictor of perioperative complications in this complex subset of patients are the patients pre-operative co-morbidities as judged by ASA class and Kaplan-Feinstein co-morbidity index.