The use of preoperative intraincisional (POII) single dose antibiotic prophylaxis has the advantage of providing extremely high concentrations of antibiotic along all layers of the wound, whilst achieving adequate systemic concentrations throughout the operation. In a single blind controlled trial, 250 patients undergoing upper abdominal surgery were randomised to receive POII cefamandole (2g) or to act as control. There was one wound infection in the POII group compared with 18 in the control group (P less than 0.001). Hospital stay was reduced by an average of one day (P less than 0.02) in the antibiotic treated group.