OBJECTIVES: Asthma is the most common chronic disease in childhood. To ensure optimal control, children must have access to necessary medications, including inhaled corticosteroids for maintenance and bronchodilators as needed. The objective was to compare asthma medication use in publicly insured social assistance children to privately insured children with asthma. METHODS: Identical case definitions were used to created public (n=12,767) and private (n=17,046) cohorts of asthmatic Ontario children aged 2-14 years using 2002 aggregate private sector claims and 1998-2001 Ontario Drug Benefits database claims. Use of bronchodilators (BD), inhaled corticosteroids (ICS), leukotriene antagonists (LA) and oral corticosteroids (OS) were compared between cohorts. RESULTS: In contravention of guidelines, 12% of social assistance children received BD monotherapy compared to 1% of privately insured children. Combined therapy of ICS+BD with or without LAs was observed in 70% of privately insured children compared to 44% of social assistance children. Despite apparently better management in the private group, OS use, indicating a severe exacerbation, was 16% in the private compared to 12% in the publicly insured group. While the average annual number of claims were similar in the private and public groups (7.3 vs. 7.1), privately insured children had more ICS claims (3.2 vs. 2.9) and fewer BD claims (2.9 vs. 3.9). CONCLUSIONS: Privately insured children appeared to be better managed than social assistance children. Differences in socioeconomic status and formulary listings may explain observed differences. Policies governing public and private drug plans must ensure adequate access to necessary medications for children with asthma.