Outcomes of surgical treatment for patients with mouth cancer can be limited by the risk of perioperative complications. This study identifies factors that predict for complications in such patients. Between 1992 and 2000, 182 patients had surgery for mouth cancer. The patient, their medical and surgical characteristics as well as perioperative complications were identified. Univariate analysis was carried out to determine which characteristics were associated with complications. Complications occurred in 85 patients (47%). Fifty-three percent of the complications were of intermediate severity and 15.6% were major. The operative death rate was 3.2%. Factors predicting complications included pre-existing cardiovascular (p<0.01) and respiratory disease (p=0.02), alcohol consumption (p<0.01), stage of disease, nature and scale of surgery, duration of surgery (p<0.01). Tracheostomies (p<0.01, OR 3.05), poor differentiation of tumour (p<0.05) and presence of extracapsular spread were predictive of complications. Patients with more complications are at increase risk of operative death or dying with head and neck cancer (p=0.04). Complications were also analysed into those that may be related to surgical technique and medical management. 113 (37%) complications were in this category. Factors influencing complications are multifactorial. Identification of risk factors allows individualised approach should improve outcome of treatment.