Sixty patients admitted to the hospital for colorectal surgery were randomly assigned to prophylaxis either with a single dose of ceftriaxone (Rocephin®) i.v. plus metronidazole given 30 min prior to induction of anesthesia or with multiple doses of ceftazidime plus metronidazole given repeatedly every 8 h up to 24 h after surgery. The overall number of infections observed with the long-acting cephalosporin ceftriaxone was 4 (2 local and 2 remote), with the short-acting ceftazidime the number was 9 (5 local and 4 remote). Neither regimen was associated with adverse reactions