Epidemiological and clinical evidence have indicated that apolipoprotein A1 and B determination can better define the lipoprotein pattern in normal subjects and in subjects with coronary heart disease. In this paper, a recent immunoturbidimetric method for routine apolipoprotein A1 and B measurement (using the Turbitimer system and commercially available antisera) has been evaluated. The precision and the accuracy of the method have been previously considered. Within-run and between-run coefficients of variation (ranging from 1.67% to 5.04%) for both assays indicate good precision of the method. Accuracy was evaluated on 2 consecutive days (n = 10 each run) using a standard serum for apolipoprotein A1 and B. The bias obtained was 3.79% for apolipoprotein A1 and 2.30% for B. Apolipoproteins A1 and B were then measured in 100 normal and hyperlipemic sera with the immunoturbidimetric assay and radial immunodiffusion (using the monoclonal antibodies). The data obtained were evaluated by linear regression analysis (Al, r = 0.893; B, r = 0.862). The good correlation between the two methods suggests that the immunoturbidimetric assay can be usefully performed for routine apolipoprotein A1 and B determination because of its lower cost, rapidity, and simplicity.