The possible causes and consequences of hypervitaminosis A and retinol binding protein (RBP) levels were investigated in patients with chronic renal disease submitted or not to dialysis treatment. The study was conducted on 20 patients divided into two groups: 10 patients with chronic renal failure (CRF) treated by continuous ambulatorial peritoneal dialysis (CAPD), and 10 CRF patients with no dialysis treatment. Ten normal subjects formed the control group. Retinol levels were determined by HPLC, and RBP levels by immunoassay in plasma and in post-dialysis fluid at different periods of time. Laboratory tests were carried out on all subjects, and dietary history was taken. Patients on dialysis had higher retinol levels than untreated patients. Retinol levels were found to be correlated with RBP levels. Serum retinol and RBP levels did not vary with diet, age or time of disease, dialysis group or time of dialysis, nor were they correlated with the levels measured in the dialysis fluid (CAPD). There was no significant correlation in retinol levels between chronic patients and controls. It is suggested that vitamin A and RBP clearances during dialysis do not accompany urea or creatinine clearance. Hypervitaminosis A did not show any toxic effect.