Background: Is the practice style of specialists overly reliant on diagnostic tests? Health maintenance organization managers and other clinicians have been critical of the high cost practice styles of specialists, but if the specialists' practice style ultimately results in similar or lower total costs because of better outcomes in the treatment of exceptional cases, then such practice styles are cost-effective and should be encouraged. Indeed, if this is the case, not employing a test-intensive practice style could be considered negligent under a legal criterion. Objective: We attempted to determine whether the care of pediatric asthmatic patients by allergists is characterized by more testing, but by better, less costly outcomes than care by non-allergists. Methods: We used administrative data on pediatric asthmatic cases from a large health care plan from 1992 to determine whether patients treated by allergists received more tests, cost more, and had fewer asthmatic management breakdowns than patients treated by non-allergists. We used regression analysis to hold constant aspects of the patient's case mix. Results: Although allergists ordered significantly more tests than non-allergists, their overall treatment costs were similar. Patients treated by allergists had fewer management breakdowns. Conclusions: These results suggest that the allergists' test-intensive practice style is cost-effective.