During the period 1971 to 1975, the cholesterol content of lipoprotein density classes were measured in 2415 male and female Framingham Heart Study participants and 4342 of their offspring and offspring spouses who were free of coronary heart disease. In this first of three papers, the univariate and bivariate distributions of high density lipoprotein cholesterol, low density lipoprotein cholesterol, and very low density lipoprotein cholesterol are presented. There are differences in the levels of lipoprotein cholesterols by age, gender, and use of hormone preparations. The bivariate cross-tabulations of the three pairs of lipoprotein cholesterol measurements exhibit properties that cannot be appreciated from univariate summary statistics and suggest the importance of joint consideration of different lipoprotein cholesterol patterns for assessing the risk of coronary heart disease.