Thirty-one patients with isocyanate-induced asthma were studied 6-54 months after diagnosis. Four had the same work conditions and unchanged or worse respiratory symptoms; seven had an alternative job or safer work conditions at the same work-place and suffered from mild to severe symptoms. The remaining twenty subjects were definitely removed from exposure; of these, ten (50%) remained symptomatic after being removed from exposure for an average of 19 months. Asymptomatic patients appeared to be younger and to have shorter durations of total and symptomatic exposures, while symptomatic patients were more reactive to acetylcholine at diagnosis. For patients removed from isocyanate exposure and for those re-employed at the same work-place, quality of the new work site seems to play a role in the evolution of isocyanate-induced asthma.