Correlates of high-density lipoprotein (HDL) cholesterol levels were studied in 4756 white males and females ages 20-59 years examined during a population survey conducted by 10 North American Lipid Research Clinics. Multivariable analysis was used to assess the relation of social, demographic, physical and behavioral characteristics for HDL cholesterol in each of the study populations and in subgroups defined by sex, age and gonadal hormone use. Characteristics associated with higher HDL cholesterol concentrations were a lean body habitus, not smoking, consumption of moderate amounts of alcohol, physical activity or exercise, membership in a high educational stratum, increased age and low dietary consumption of sucrose and starch. Each of these characteristics was examined in detail in its relation to HDL cholesterol concentrations in the respective chapters in this monograph; the purpose of the study reported here was to summarize the findings. When all variables were considered simultaneously in the analysis, body mass, cigarette smoking and alcohol consumption were the attributes most strongly and consistently associated with HDL cholesterol concentrations in the populations examined. These empirical findings from a cross-sectional study replicated across diverse populations were used to derive speculative estimates of the potential for modification of population levels of HDL cholesterol, consistent with hygienic intervention and lifestyle changes. The results of the study were considered in the context of the literature on determinants of HDL cholesterol.