In normal humans and in patients with chronic renal failure (CRF), acidosis increases whole-body protein degradation. Correction of acidosis reduces protein degradation. The mechanisms underlying these changes in protein metabolism are unclear. However, one possibility is that dietary protein intake is reduced in acidosis and that this causes increased protein degradation. This possibility has not been tested. In this study the effects of acidosis on protein intake in patients with CRF have been assessed using 7-day weighed dietary inventories in the acidotic state (venous bicarbonate 15.6 +/- 1.0 mmol/L) and following treatment with oral sodium bicarbonate (venous bicarbonate 21.0 +/- 1.4 mmol/L). Protein intake was also derived from urinary nitrogen excretion. There was no significant difference in protein intake calculated from dietary records (1.0 +/- 0.09 g/kg/d v 1.06 +/- 0.1 g/ kg/d) or calculated from urinary nitrogen (1.13 +/- 0.07 g/kg/d v 1.06 +/- 0.06 g/kg/d) between the untreated and bicarbonate-treated states in eight patients with CRF. We conclude that acidosis in CRF patients does not affect dietary protein intake and that dietary changes therefore do not contribute significantly to the changes in protein metabolism seen in acidosis.