The Los Angeles “Know Your Body” (KYB) program is an organized health education activity for children designed to encourage positive health behavior and discourage or interrupt behavioral patterns that are linked to illness, injury, disability, or death. Components of KYB include a 20-week curriculum; a survey of health knowledge, attitudes, and behaviors; in-service training for elementary school teachers; and a clinical screening that provides feedback to students on selected indices. As part of a KYB field demonstration in Los Angeles conducted by the UCLA Division of Cancer Control, Jonsson Comprehensive Cancer Center, 1,503 Los Angeles and Santa Monica-Malibu children ages 9–11 in grades 4 and 5 underwent baseline health screening evaluations in March 1981, measuring height, weight, triceps skinfold thickness, serum cholesterol, pulse rate recovery following exercise, and blood pressure. The population mean for serum cholesterol was 182.6 mg/dl, with no significant racial/ethnic, sex, or age differences. Significant racial/ethnic differences were found in obesity, with Hispanics having the highest prevalence, Asians the lowest. Black students scored significantly higher in pulse rate recovery following exercise, suggesting better relative cardiovascular fitness, and Asians scored lowest. Blacks were more likely to exceed the 95th percentile in diastolic and systolic blood pressure. Overall, 48% of the children had one or more chronic disease risk factors.