Occupational asthma (OA) is a useful model for the study of asthma in humans. The possibility that inhaled corticosteroids, in addition to withdrawal from the workplace, could improve clinical and functional recovery from OA can be hypothesized. We assessed clinical, functional, and behavioral characteristics of 32 subjects (22 male, 10 female), in all but one of whom OA was confirmed by specific inhalation challenges induced by either high- (n=13) or low-molecular-weight (n=19) agents within 3 mo after cessation of exposure. In this randomized, crossover, double-blind study, subjects (paired for baseline PC20 and duration of symptoms after exposure) received either placebo or 1,000 micrograms of inhaled beclomethasone daily for 1 yr, followed by the alternate medication for 6 mo. Various clinical, functional, and behavioral parameters were examined at each 3-mo visit. Significant improvement in clinical (nocturnal symptoms, cough), functional (morning and evening peak expiratory flow rates), and behavioral (quality of life) parameters were detected in the active-treatment period, although the magnitude of the improvement was relatively small. Side effects (oropharyngeal, reduced cortisol) were similar in the placebo and treatment groups. Distinguishing subjects who started with the active preparation from those who were given placebo first showed that most clinical and behavioral parameters improved in the former instance, whereas there was no significant difference in the latter. We conclude that inhaled corticosteroids induce a small but significant overall improvement of the asthmatic condition in subjects with occupational asthma caused by high- and low-molecular-weight agents after withdrawal from exposure. The beneficial effect is, however, more pronounced if inhaled steroids are given early after diagnosis.