OBJECTIVE: To evaluate the longitudinal impact of asthma specialist care on the risk of emergency department (ED) visits and hospitalization for asthma. DATA SOURCES/STUDY SETTING: A prospective cohort study using both telephone survey and computerized utilization data. STUDY DESIGN: We recruited a prospective cohort of 4,742 adult members of a closed panel managed care organization who were hospitalized for asthma (the ‘baseline hospitalization’). DATA COLLECTION/EXTRACTION METHODS: Visits to asthma specialists were ascertained from computerized utilization databases. Specialist visits after baseline hospitalization were defined as time-dependent covariates. An alternative analysis defined specialist visits during the year preceding baseline hospitalization. A subcohort of 596 subjects completed telephone interviews. PRINCIPAL FINDINGS: Compared with subjects who received no specialist visits after baseline hospitalization, treatment by allergists (hazard ratio (HR) 1.04; 95 percent confidence interval (CI) 0.87-1.26) or pulmonologists (HR 0.92; 95 percent CI 0.71-1.19) was not associated with a reduction in the risk of future ED visits for asthma in the entire cohort, controlling for age, sex, race, recent asthma medication dispensing, and pharmacy benefits status. There was also no association between allergist visits and the risk of subsequent hospitalizations for asthma (HR 0.93; 95 percent CI 0.75-1.14). In contrast, visits to pulmonologists (HR 0.74; 95 percent CI 0.55-0.99) were related to a reduced risk of rehospitalization. CONCLUSIONS: Pulmonary specialist visits appeared to reduce the risk of hospitalization for asthma, whereas asthma specialist visits did not reduce the risk of ED visits. In the context of comprehensive prepaid health care, the benefit of specialist care was modest.