OBJECTIVES: To investigate the effect of physical activity on the association between television viewing and overweight (body mass index (BMI)  25 kg/m2). DESIGN: Cross-sectional study administered by interview to adults randomly selected from the electronic white pages. SUBJECTS: 3392 adults (64% response rate) from a representative population sample in the State of New South Wales, Australia. MEASUREMENTS: Self-reported height and weight, two-week leisure-time physical activity recall, one-week average television viewing recall. RESULTS: BMI and physical activity patterns were both associated with hours of television watched. Compared to those participants who reported watching less than one hour of television per day, those watching 1 to 2.5 hours were 93% more likely to be overweight (BMI25 kg/m2), those watching 2.5 to 4 hours were 183% more likely to be overweight, those watching more than 4 hours per day were four times more likely to be overweight. Physical activity was not directly associated with being overweight, but an interaction between activity and television watching was present. Respondents in the low, moderate and high physical activity categories who reported watching more than 4 hours of television per day were twice as likely to be overweight compared to those who watched less than one hour of television per day, irrespective of physical activity participation. CONCLUSIONS: With approximately half the Australian adult population overweight or obese, these findings indicate that public health strategies to reduce overweight and prevent weight gain may need to focus on reducing sedentary behaviours such as television viewing in addition to increasing physical activity. International Journal of Obesity (2000) 24, 600-606 | 
