In Australia, the prevalence of male adolescent overweight or obesity has increased dramatically over the past two decades. Currently, there are no multi-faceted obesity prevention programs that are targeted towards male adolescents. The FILA (Fitness Improvement, Lifestyle Awareness) program was developed to address many of the shortfalls in the literature. The FILA feasibility trial was conducted in an Independent Boys School in Sydney, Australia, during Terms 2 and 3 2006. The program is a multifaceted 16-week intervention focusing on: increasing cardio-respiratory fitness and physical activity and increasing healthy eating and reducing small screen recreation through behaviour modification techniques. The primary outcome measure was cardio-respiratory fitness. Secondary outcomes included BMI, waist circumference, time spent in small screen recreation and quality of life. All outcomes were assessed at pre- and post- (16-weeks) intervention. The trial was deemed feasible: evidenced by successful recruitment and retention rates; acceptable: evidenced by strong participant enjoyment and parent and staff satisfaction; and potentially efficacious through participant changes in outcomes from pre- to post- intervention. Paired samples t-tests revealed a significant improvement in cardio-respiratory fitness (t=3.97; p=0.001) and quality of school life (t=3.32; p=0.005) and a small, but non-significant improvement in waist circumference (t=1.61; p=0.13) and weekend small screen recreation time (t=0.67; p=0.513). The FILA feasibility trial results are highly promising demonstrating the feasibility, acceptability and potential efficacy of implementing a multi-faceted program within the school curriculum to improve cardio-respiratory fitness and prevent excess weight gain in adolescent males. A pilot RCT will be conducted in 2007.