In recent years, the determination of homocysteine (Hcy) has become increasingly important, since high levels of Hcy in plasma or serum represent an independent risk factor for occlusive vascular diseases. Nowadays, clinical laboratories use several analytical techniques to measure Hcy, of which high-performance liquid chromatography (HPLC) is the most popular. Recently, assays for Hcy quantification based on enzyme immunoassays (EIA) have become commercially available. Our group carried out the validation of the Axis method and compared results with those obtained by an established HPLC assay. Intra- and inter-assay coefficients of variation were < or = 8.5%. Compared with HPLC, linear regression analysis showed r=0.984, slope=0.952, intercept = 1.24 /mol/l; Bland-Altman procedure, the mean of the difference EIA-HPLC results = 0.5 micromol/l. Our results suggest that Hcy determinations by both methods are equivalent, and that the Axis assay provides reproducible and reliable data.