Aims: Australian guidelines recommend that children participate in at least one hour of physical activity every day. We aimed to measure physical activity participation in a random sample of Australian primary school children and to determine the biological, behavioural, environmental and social influences associated with insufficient daily activity. Method: We analysed the following cross-section data from a randomly selected sample of children (N = 518) aged 5 to 12 years: age, gender, socioeconmic status (SES) indicators, family size, home play equipment availability, transport method to school, and estimated time per week in physical and sedentary activity. Logistic regression analysis was performed to determine variables that were associated with insufficient (<60 minutes) daily activity. Results: Seventy-six children (15% of the cohort) failed to meet the minimum activity recommendations of 60 minutes of daily activity. These children were significantly less likely to walk or cycle to school (adjusted odds ratio (OR) 0.43; 95% CI = 0.24 - 0.77) or participate in organised sports or activity (OR 0.42; 95% CI = 0.28 - 0.64) and were more likely to spend in excess of 2 hours a day watching television of using a computer for entertainment (OR 2.10 (1.16 - 3.78). Age, gender, SES and family size were not significantly associated with insufficient activity. Conclusion: There exists a significant proportion of the paediatric population who are insufficiently active. Interventions to encourage increased activity in this sub-group may be successful if they seek to alter sedentary behaviour (namely television use) and method of transportation to and from school.