This study is a comparison of certain factors related to leanness, obesity, and "average" weight in 12 healthy preadolescent girls of above-average intelligence and similar family backgrounds. Factors considered were anthropometric data from the subjects, possible height-weight relationships between subjects and parents, 7-day calorie intakes of the subjects, 7-day activity records and certain eating practices of the subjects and parents, and some personality components and activity interests or the subjects as measured by standardized tests. The subjects, ranging in from eight to 10 years, were selected according to the physique appraisals of lean, heavy, and "average.” Mean weights of the lean, heavy, and “average” subjects, respectively, were 23.4 kg, 43.0 kg, and 27.8 kg. Corresponding mean percentage deviations from standard height-weight criteria were 18.7 percent underweight, 29.5 percent overweight, and within 4.9 percent of the standard. Eight additional anthropometric findings supported these physique appraisals. Calculated mean daily caloric intakes for the lean, heavy, and "average" subjects, respectively, were 2193 calories, 1925 calories, and 1761 calories. Reported activity patterns suggested that the lean subjects and their parents were the most physically active, while the heavy subjects and their parents were the least active. These findings for the subjects were supported by their scares in a standardized interest inventory. A tendency toward obesity in the subjects studied was more related to lack of interest and participation in physical activities than to excessive caloric intake. / Master of Science