A randomised controlled trial of the effects of two different physical activity programmes on coronary heart disease (CHD) risk factors, academic performance, and classroom behaviour, was conducted on over 500 children (mean age 10) in eight Adelaide primary schools in 1978. During a fourteen-week intervention period classes were involved in either: an endurance fitness programme, a skills programme, or participated as controls. The Fitness group experienced significant gains in physical work capacity and decreases in body fat compared to the Control and Skill groups. Diastolic blood pressure decreased significantly more in the Skill group than in the Control; but no significant difference was observed between the Fitness and Control groups. Changes in the other CHD risk factors measured, systolic blood pressure, plasma cholesterol, triglycerides and HDL cholesterol did not differ between groups. Both the Fitness and Skill groups demonstrated improvements in classroom behaviour compared to the control group; but no differences in academic performance were observed.