A 26-member kindred had the newly recognized heritable hyperlipoproteinemia, familial hyperalphalipoproteinemia. In affected family members, hyperalphalipoproteinemia was not secondary to any diseases, drugs, or industrial exposures known to elevate α-lipoprotein (high-density) cholesterol (C-HDL) levels. Hyperalphalipoproteinemia was transmitted vertically through three generations. There were five matings of hyperalphalipoproteinemic to normal individuals, with 25 offspring. The ratio of offspring with elevated C-HDL levels to those with normal C-HDL levels was 12:13 (0.923), a ratio not significantly different from 1 (X2=0.04), the ratio predicted for an autosomal dominant trait. In affected kindred members, levels of total plasma cholesterol were slightly elevated, those of low density lipoprotein cholesterol were normal to low, those of triglyceride were normal, and those of C-HDL were consistently elevated. Affected subjects were healthy, without xanthomata, and had no unique physical or neurological features.