The relation between multiparity and lipid and lipoprotein levels was examined in aa sample of 1275 Rancho Bernardo women aged 50-89. Number of pregnancies ranged from 0 to 13 with aa mean of 2.1. Pregnancy was unrelated to high density lipoprotein cholesterol level in women with 4 or fewer pregnancies, but women with 5 or more pregnancies had significantly lower levels both before and after adjustment for age, obesity, diabetes, alcohol and cigarette consumption, exercise and estrogen use. After multiple regression analysis, women with 5 or more pregnancies had high density lipoprotein levels that were 4.9 mg/dl lower than women with 4 or fewer pregnancies. No differences in total cholesterol, low density lipoprotein cholesterol or triglyceride levels were observed by number of pregnancies. If confirmed by others, these results suggest that one factor mediating the previously reported relationship between multiparity and cardiovascular disease may be aa decreased level of high density lipoprotein cholesterol.