Results of a multicenter evaluation of automated assays for measurement of apolipoproteins (apo) A-I and B with the Paramax analytical system are reported. Apo A-I and apo B response surface models were used to optimize concentrations of critical assay variables. Overall imprecision for apo A-I controls at concentrations of 1.01-1.61 g/L was 3.7-6.6%; overall imprecision for apo B controls at 1.00-1.61 g/L was 2.8-6.9%. There was no interference in apo A-I measurements. Albumin concentrations > 59 g/L resulted in a negative interference, and collection in sodium heparin caused a positive interference in apo B results. Apo A-I and apo B assays demonstrated acceptable agreement with comparative methods, although the Paramax apo B assays had a negative bias with respect to comparison methods. In 116 healthy individuals, serum apo A-I ranged from 0.97 to 2.05 g/L and serum apo B ranged from 0.51 to 1.32 g/L.