Troleandomycin has been reported to be useful for reducing the steroid requirement of patients with asthma. The purpose of this study was to evaluate the usefulness of troleandomycin in treating patients with steroid-dependent asthma as well as in patients with steroid-dependent chronic obstructive pulmonary disease (COPD). Twelve patients with obstructive airway disease were studied; 6 patients had a diagnosis of asthma, and 6 patients had COPD. All had failed previous attempts to reduce their dosage of steroids. Among the patients with asthma, it was possible to taper methylprednisolone dosage from 29.3 +/- 21.8 mg to 11.1 +/- 7.4 11.1 mg (P less than .05). In the group with COPD there was also a significant decrease in steroid dosage--from 22.6 +/- 12.2 to 6.0 +/- 4.5 mg. These changes were not associated with a decline in spirometric values; nor was improvement secondary to improved theophylline levels, as demonstrated by a significant decrease in serum theophylline levels from 12.4 +/- 3.6 mg/dL baseline to 8.5 +/- 2.8 mg/dL (P less than .001) after maximal steroid tapering. We conclude that troleandomycin is effective in reducing the steroid dosage in patients with COPD or asthma.