1. Patients having regular dialyzation treatment have a 50% physical performance, as compared with the common population matched for age, already at the onset of treatment. 2. Physical performance does not depend on the level of residual glomerular filtration, on the mean urea concentration in the course of dialyzation treatment and the variations of urea concentrations during dialysis and intervals between dialysis. 3. Physical performance of patients having regular dialyzation treatment depends in a significant way on nutrition. 4. While during renal disease the performance of patients declined by 43%, in the course of ten years of regular dialyzation treatment it declined only by 21%. This fact indicates that already during the period of conservative treatment the patients should have an adequate diet and should engage in exercise to keep fit. Also during regular treatment, in addition to adequate dialysis, the patients should have an adequate diet and an opportunity to engage in physical exercise.