In 158 uraemic patients on haemodialysis complaints resembling Raynaud's disease were observed more frequently (85 patients = 54%) than in an equal number of age and sex matched control persons (10 probands = 6%). The complaints were also registered in the arm without the fistula. Triggering causes were exposure to cold or isometric muscular exercise. The complaints were slightly more frequent in women and occurred in 28% prior to dialysis in the terminal stage of renal insufficiency. They were improved only in a minority of those treated with haemodialysis, however they disappeared after successful renal transplantation. Veno-occlusive plethysmographic investigations showed that in asympatomatic patients the resting perfusion at room temperature, the perfusion in reactive hyperaemia, and perfusion at 0 degrees C were not different from control persons. Patients with Raynaud's phenomenon had on average a diminished resting perfusion and a normal perfusion after reactive hyperaemia. The perfusion at 0 degrees C was lower than in asymptomatic patients but still higher than in patients with Raynaud's disease. Increased cooling of the skin and delayed rewarming were objectively measured by using skin temperatures. There was not correlation between the complaints or perfusion values and the vibration threshold.