This study was carried out in seven patients being treated by intermittent hemodialysis. Each had some residual renal function. In protocol 1, when the patients were dialyzed weekly and the dietary protein intake was 0.96 g/kg/day, the nitrogen balance corrected for changes in the urea pool was positive during the days between dialysis; the serum urea concentration (SUN) before dialysis was 109 +/- 7 mg/dl. In protocol 2, when dietary protein was reduced to 0.4 g/kg/day and supplemented with essential amino acids (10 g/day), the corrected nitrogen balance on days between weekly dialyses was positive; the SUN before dialysis was lower than it was in protocol 1 (-33 +/- 7 mg/dl, P less than 0.01). The nonurea space (body weight minus body water) increased in six of seven patients during protocol 2. Two patients were then treated with the dietary regimen of protocol 2 and dialyzed every 2 weeks. The corrected nitrogen balance on nondialysis days was positive, and there was a further increase in nonurea space. This study suggests that dialysis frequency may be reduced in some patients with residual renal function by means of nutritional therapy.