This study assessed family physicians' and pulmonary specialists' approaches to the treatment of adult outpatient asthma using a self-administered questionnaire consisting of six asthma scenarios of varying severity levels. One hundred sixty-three randomly selected family physicians and pulmonary specialists completed the questionnaire (response rate of 80%). We observed that, regardless of asthma severity, more than 75% of physicians (regardless of specialty) would not include oral theophylline or nonsteroidal anti-inflammatory preparations in their treatment approach. Pulmonary specialists' and family physicians' approaches to mild asthma were similar (more than 90% recommended an inhaled beta2-agonist). However, considerable differences existed among and between physician groups for the remaining scenarios. For example, with an exacerbation associated with an upper respiratory tract infection, family physicians were more likely to recommend oral antibiotics (p<0.0001) and a same-day outpatient visit (p<0.0001), whereas specialists were more likely to increase the inhaled corticosteroid dosage (p<0.0001). Overall, disagreement was observed almost twice as often among family physicians than among specialists. Our results suggest that physicians vary markedly in their reported use of most interventions available to treat asthma, even when the disease severity is specified.