Procalcitonin (PCT) is regarded as a specific indicator of bacterial infection. Infectious complications in patients after colorectal surgery are a common cause of morbidity and mortality. The aim of this study was to investigate (a) whether PCT could serve as a negative predictive marker for postoperative complications and (b) whether, in patients with elevated PCT levels, a pre-emptive treatment with the third-generation cephalosporin ceftriaxone is superior to an antibiotic treatment starting later on the appearance of clinical signs and symptoms of infection.