Willem Kolff (1911-2009), son of a physician, studied medicine in Leiden and specialised in internal medicine in Groningen. It was there that he started attempts to apply the phenomenon of dialysis in patients suffering from renal failure. He built the first prototypes of dialysis machines after his appointment as an internist in the municipal hospital in Kampen, during the Second World War. Indeed, in the first 15 patients he managed to decrease urea levels, resulting in temporary clinical improvement, but eventually they all died. It was not until after the war that dialysis helped a patient survive an episode of acute glomerulonephritis. After 1950 he continued his work on artificial organs in the United States (first in Cleveland and later, after 1967, in Salt Lake City). Although most of his work from then on revolved around the development of an artificial heart, he also contributed to the design of a compact, disposable apparatus for dialysis, the 'twin coil'. Haemodialysis also became feasible for patients with chronic renal failure after the 'Scribner shunt' (1960) provided easy access to the circulation. Peritoneal dialysis is another option. Excess mortality, mainly from cardiovascular disease, is still a largely unsolved problem