Perioperative fluid therapy and associated outcomes of patients undergoing major elective open gastrointestinal surgery are poorly understood. This study measured perioperative fluid therapy, complication rates and outcomes for major elective open gastrointestinal surgery in a tertiary care hospital. We obtained demographic data, operative details, fluid prescription, complications and outcomes in 100 patients. Patients were elderly and had multiple comorbidities. Median delivered intraoperative fluid volume was 4.2 litres, followed by 6.3 litres over the subsequent 24 hours. Perioperative fluid prescription was associated with a positive fluid balance. Complications occurred in 57% of patients with 32% experiencing at least one major complication. Serious complications were substantially more frequent in patients having non-colorectal operations. The most common adverse events were pulmonary oedema (21%), ileus (18%), serious sepsis (17%), pneumonia (17%), arrhythmias (14%), delirium (14%) and wound healing problems (infections 13%, anastomotic leaks 12%). Mortality at 30 days was 2%. This study provides planning data for future interventional studies.