The impact of the pre-operative nutritional and clinical state on post-operative morbidity and mortality is not fully known and the effect of total parenteral nutrition (TPN) on the postoperative complication rate has not been established. We have investigated the effects of postoperative TPN on the complication rate in 92 patients after major colorectal surgery for carcinoma of the large bowel or inflammatory bowel disease in a controlled, randomised study. The complication rate was analysed against seven commonly used nutritional (biochemical and anthropometric) variables and against the diagnosis, clinical inflammatory activity and presence of pre-operative septic complication. Patients were randomly allocated to postoperative TPN or conventional fluid and electrolyte support. The results show no correlation between the complication rate and the nutritional and clinical state of the patients as assessed pre-operatively. The complication rate was not significantly reduced by postoperative TPN. This study indicates that biochemical and anthropometric nutritional variables do not identify patients at risk to develop postoperative complications. The presence of pre-operative complications showed a marginal correlation with postoperative morbidity, in agreement with previous experience. The result of this study obviates the use of TPN in routine postoperative care.