Acute kidney injury following cardiac surgery (AKICS) remains a frequent cause of major morbidity and mortality. The aim of this study was to examine the influence of timing of dialysis. A retrospective analysis of 3528 patients undergoing cardiac surgery between April 1995 and July 2006 was performed. In group 1 (April 1995-January 2000) intermittent haemodialysis was resorted to when other supportive measures failed. In group 2 (January 2000-July 2006) intermittent haemodialysis was commenced immediately when oliguria did not respond to fluid replacement or single-dose diuretics. In group 1, 49/1511 (3.2%) patients developed AKICS. Thirty-four patients did not receive dialysis and six patients died (18%). Of the remaining 15 patients who underwent dialysis, 13 died (87%). The overall mortality for group 1 AKICS patients was 19/49 (39%). In group 2, 87/2017 (4.3%) patients developed AKICS. Thirty-one patients did not require dialysis and none died. Of the 56 patients who were dialysed, 14 died (25%). During January 2005-July 2006, mortality following dialysis fell further to 17% (4/24). The overall mortality for group 2 patients developing AKICS was 14/87 (16%). Although the incidence of AKICS increased from 3.2% to 4.2%, earlier dialysis resulted in significantly improved survival (P=0.00001).