A radial immunodiffusion assay (RID) for quantitation of human serum apolipoprotein CII (apoCII) was developed. Antiserum to apoCII was raised in goats with purified apoCII. The antibody-gel plate was prepared with 1% agarose. 5 microliters of each sample or standard serum was added in a well. Diffusion was performed at 25 degrees C or 37 degrees C for 48 h. The standard curve with a working range of 0.8-4.5 mg/dl was plotted. The minimum measurable concentration of apoCII was 40 ng. The intra-assay and inter-assay CV were 1.4-3.5% and 1.3-3.6% respectively. The recovery of the assay was 92.38-104.35%. The concentrations of apoCII for healthy adults and patients with hyperlipidemia were 3.9 +/- 1.7 mg/dl (M +/- SD, n = 67) and 5.9 +/- 2.5 mg/dl (n = 43) respectively.