The authors investigated possible differences between specialists and generalists in the intensity with which they treat patients with asthma by studying the care of 283 patients between the ages of six and 40 provided by 13 allergists and 40 randomly selected physicians in two primary care specialties: pediatrics and family practice. After excluding patients with more than one physician, allergists' patients were nearly identical to primary care physicians' patients in the frequency and duration of symptoms, and they had a similar number of asthma-related emergency room visits in the previous year and asthma-related hospitalizations in the preceding 3 years. The allergists treated their patients significantly more intensively than did the primary care physicians. Sixty-two percent of allergists' patients had received oral corticosteroids in the preceding year compared with 30% of primary care patients (P less than 0.001). More of the allergists' patients had received oral corticosteroids throughout the year (9% vs. 0%, respectively, P less than 0.01). They were also more likely to have used corticosteroid inhalers (46% vs. 19%) and a greater number of asthma medications (mean = 2.8 vs. 1.3). In a separate survey of the same physicians, using clinical vignettes, the allergists were more likely to prescribe corticosteroid tablets and inhalers. These findings suggest that specialists and generalists differ in the intensity with which they treat patients with asthma and cannot be explained by patient selection or severity differences.