Serum concentrations of total cholesterol, triglycerides, and apolipoproteins (apo) A-I, B, CII, CIII, and E in 36 hemodialysis patients and nine anephric patients were compared with the concentrations in 34 normolipidemic subjects. The dialysis patients displayed a moderate hypertriglyceridemia (1.94 +/- 0.12 vs 1.09 +/- 0.11 mmol/L in controls, mean +/- SEM; P less than 0.001), apo CIII concentrations were also increased (130.2 +/- 2.1 vs 108.4 +/- 0.7 mg/L; P less than 0.001), whereas apo CII (34.5 +/- 0.5 vs 36 +/- 0.5 mg/L; P less than 0.05), apo E (22.7 +/- 0.3 vs 27.9 +/- 0.2 mg/L; P less than 0.001), and apo A-I (1.18 +/- 0.05 vs 1.31 +/- 0.04 g/L; P less than 0.05) were decreased. Concentrations of serum apo B were normal (0.86 +/- 0.03 vs 0.97 +/- 0.07 g/L). In the hemodialysis patients, apo CIII concentrations were increased in apo B-containing lipoproteins (30.1 +/- 0.5 vs 25.0 +/- 0.1 mg/L; P less than 0.001), whereas CII and E were decreased below control values (14.4 +/- 0.2 vs 16.8 +/- 0.1, and 8.2 +/- 0.2 vs 11.4 +/- 0.1 mg/L, respectively; P less than 0.001 each). By calculation, non-B-containing lipoproteins in the hemodialysis group had increased concentrations of apo CIII (100.1 +/- 2.1 vs 83.3 +/- 0.7 mg/L; P less than 0.001) and decreased amounts of apo E (14.5 +/- 0.4 vs 16.4 +/- 0.3 mg/L; P less than 0.001); apo CII content was unchanged (20.1 +/- 0.5 vs 19.3 +/- 0.5 mg/L). Results for apo CII, CIII, and E among apo A-I-containing lipoproteins in both normolipidemic and hemodialysis groups were similar to those in non-B-containing lipoproteins. Finally, the sole significant (P less than 0.01) difference between the anephric and hemodialysis groups was the lower apo E concentrations in the former group. Accumulation of triglyceride-rich lipoproteins in hemodialysis patients may thus be related to the enrichment of apo CIII in apo B-containing lipoproteins and to a marked decrease in the apo CII and E contents.