To assess the suitability of latamoxef (moxalactam) as single agent chemoprophylaxis in elective colorectal surgery, 120 consecutive patients were randomized to receive latamoxef (L) 1 g or cephazolin 1 g and metronidazole 500 mg (CM) administered intravenously at induction of anaesthesia and 6 and 12 h postoperatively. The groups were well matched for age, sex, pathology and procedures. Serum and tissue levels of latamoxef were well above the MIC90 for most bowel organisms. Inpatient stay was similar for both groups. Pyrexia was seen in 44 patients (11 L, 23 CM) and eight developed a wound infection (3 L, 5 CM). Major intra-abdominal sepsis occurred in seven patients (2 L, 5 CM), secondary to anastomotic leakage in four (1 L, 3 CM). Twenty patients developed a chest infection (5 L, 15 CM) and eight urinary sepsis (2 L, 6 CM). No bleeding complication occurred, and there was no difference in clotting function between the two groups. Six patients died prior to follow-up at six weeks (1 L, 5 CM), two from anastomotic dehiscence. All but three wounds had healed (1 L, 2 CM) and one further patient had an incisional hernia (CM). These results suggest that latamoxef is an efficient chemoprophylactic agent in elective colorectal surgery, and is marginally better than cephazolin plus metronidazole.