Mexican-Americans represent the single largest component of the US Hispanic population and have been shown to bear a disproportionate burden of chronic disease. A representative sample of 1,004 Mexican-Americans aged 15-74 years from Starr County, Tex., was recruited for this study. Each subject was provided a detailed physical evaluation that included measurement of fasting levels of cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol and its subfractions (HDL2 and HDL3) alpha- and beta-lipoprotein cholesterol, and low density lipoprotein cholesterol. Apolipoproteins A-I, A-II, B, C-II, C-III, and E were determined for approximately 550 of these individuals. Age- and sex-specific mean levels and percentile cut points are presented. The distributions of lipoproteins are quite similar to those of the general population except for consistently higher triglycerides in males and females and lower HDL cholesterol levels in females. These findings are consistent with the high frequency of obesity. Comparative age- and sex-specific data for the apolipoproteins are not widely available. Where such data exist, apolipoprotein levels observed in the Mexican-American population tend to be similar to or lower than the comparative data.