This report presents estimates of the distributions of selected behavioral patterns of children 6-11 years of age in the noninstitutional population of the United States by age and sex. Findings are based on parents' ratings on a self-administered and a trained interviewer-administered medical history of children, which were examined in the Health Examination Survey of 1963-65. A probability sample of 7,417 children was selected. Ninety-six percent of the sample examined were found to be closely representative with respect to age, sex, race, region, and other available demographic and socioeconomic variables. Included are data on key aspects of early development concerning general behavior, sleep and eating behavior, peer relations, behavior problems, the extent of responsibility in the home, the extent of participation in organized activities, and general use of time. Whenever possible, comparison was made with findings from previous studies. (A 23-item bibliography and 3 tables are included.) (PD)