This double-blind parallel trial evaluated the efficacy of cloprednol, a new synthetic glucocorticoid, in 40 patients with asthma. Patients kept daily records of wheezing, chest tightness, shortness of breath and cough. Analysis of these records showed cloprednol to be statistically significantly better than placebo for the relief of these symptoms (p values ranged from less than 0.01 to less than 0.0001). Weekly physician evaluations of asthma severity, symptoms since last visit and number of asthma attacks also showed a significant drug effect in favor of cloprednol. These subjective findings were confirmed by objective pulmonary function tests (FEV1.0, FVC and PEFR). There was a statistically significant difference favoring cloprednol for all the pulmonary function measurements. Previous studies have suggested that at equipotent anti-inflammatory doses cloprednol is less suppressive of hypothalamic-pituitary-adrenal axis function. Although plasma cortisol levels were not measured in this trial, none of the patients manifested clinically important side effects which required termination of their participation in the study.