Clinical experience indicates that many wound infections present relatively late after cardiac surgery. Hence, timing may be an important issue in using this outcome as a clinical indicator. A database of 1000 patients who underwent cardiac surgery was accessed to ascertain baseline characteristics, the type of surgery, and the time of presentation of wound infections. The overall incidence of wound infection was 5.9% (59/1000). Only 36% (21/59) of the wound infections presented while the patient was in hospital. Diabetics were more likely to have a late presentation of a wound infection (the median time of presentation of wound infections (more than 17 days), i.e. 10/29 (33.4%) versus 98/971 (10.1%), Fisher's exact test P < 0.01). Wound infection can only be regarded as a reliable clinical indicator after cardiac surgery if patients are reviewed with care for 6 weeks after surgery.