This article offers a brief and personal account of the historical background, implementation and principal findings from the Trois-Rivieres regional project, a large-scale quasi-experimental intervention that tested the impact of providing a daily hour of specialist-taught quality physical education upon the physical and mental development of primary school students. The intervention continued in grades one through six, and it enhanced maximal aerobic power, physical working capacity, muscle strength and physical performance in both boys and girls in both an urban and a rural setting. However, the programme had little influence upon the immediate health, growth, maturation or prevalence of obesity in the experimental group. A follow-up study was carried out when the students had become adults; this showed positive effects upon attitudes towards physical activity, but only limited long-term effects upon habitual physical activity and other aspects of health behaviour. Strengths and limitations of the Trois-Rivieres regional project are considered, and suggestions are offered for those planning future studies of this type. (Contains 4 tables.)