Until relatively recently surgeons were familiar with the concept that some of their patients admitted to the intensive care unit require dialysis to deal with the development of severe acute renal failure. Under such circumstances the nephrology team would then attend the patient and take over that aspect of management. More recently, however, this situation has undergone a significant evolution because of the advent of continuous renal replacement therapy (CRRT). First introduced as "last ditch" therapy in the most critically ill patients who were hemodynamically intolerant of hemodialysis, CRRT has become more and more widely used. It is now the dominant form of artificial renal support in Australia and close to being the dominant treatment of the severe acute renal failure of critical illness in most European countries. The use of CRRT in the United States is rapidly growing. The arrival of CRRT has also renewed interest in the wider concept of blood purification during critical illness. Experimental and preliminary human data suggest that such blood purification therapies may indeed have beneficial immunomodulatory effects. Accordingly, CRRT is now being considered as a potential adjuvant treatment of septic shock and has even moved into the operating room as a tool for antiinflammatory therapy and volume control. The intensivist-surgeon and the general surgeon need to be aware of and understand these developments in extracorporeal therapy if they wish to make the full armamentarium of modern treatment available to their sickest patients.