Most data about the course of occupational asthma after removal from exposure are based upon the longitudinal assessment of employees exposed to substances inducing late asthmatic reactions in bronchial provocation tests. It was the aim of this study to describe the course of immediate-type occupational asthma after allergen avoidance. Twenty-four platinum refinery workers were examined on two occasions. All subjects reported work-related asthma while they worked in the refinery department. The diagnosis of platinum salt asthma was established by a positive bronchial challenge test with hexachloroplatinic acid in each case. Eleven of the 24 subjects were still exposed to platinum salts at the time of the first investigation, but all had been removed from exposure for 19 mo (1 to 77) on the second investigation. Asthma was still reported by 17 subjects, and all but two showed bronchial hyperresponsiveness (PC50SGaw < 8 mg/ml) on the second investigation. Bronchial responsiveness to methacholine, skin reactivity, and bronchial responsiveness to platinum salt, as well as FEV1, did not change between assessments. Total serum IgE decreased from 126 to 103 U/ml (p < 0.005). Analysis of variance showed no association of the individual differences in PC50 (methacholine) between both investigations with smoking, time from the onset of symptoms to removal, time from removal to the first or second investigation, skin sensitization to environmental allergens, or total IgE. We conclude that both nonspecific and specific bronchial responsiveness do not decrease after removal from exposure in immediate-type asthma caused by platinum salts.