BACKGROUND: The Tonga Asthma Self-management Project assessed whether the introduction of an asthma self-management plan would reduce asthma morbidity. METHODS: The project involved a 'before and after' trial, with each participant serving as his/her own control. Asthma patients used the self-management plan to manage their asthma medication or obtain medical help based on their peak expiratory flow (PEF) rate and/or asthma symptoms. RESULTS: The 110 participants initially had relatively high asthma morbidity: 68% had had an emergency medical visit for asthma in the previous 12 months. Ninety-two (84%) completed the 12-month programme. Emergency doctor visits fell from 66% in the previous 12 months to 18% (P < 0.001) in the following 12 months. Other measures also improved, including hospital admissions (from 19% to 3%, P = 0.001), having 14 days or more 'out of action' (from 29% to 4%, P < 0.001), waking > or = 2 nights a week (from 40% to 13%, P < 0.001), severe asthma attacks (from 54% to 18%, P < 0.001) and mean PEF rates (from 341 l/min to 417 l/min, a 22% increase, P < 0.001). CONCLUSIONS: The potential benefits of asthma self-management plans and community-based asthma education are supported by the findings of the Tonga study. Their implementation is essential in the resource-scarce Pacific health setting.