1. After having reviewed all the 22 patients in Belgium who are indemnified for isocyanate occupational asthma, the authors cannot find any significant factor that would permit screening and previous eviction (atopy, smoking habits). Every patient suffers from a non-specific bronchial responsiveness even after the end of exposure. 2. The specific RAST HDI, MDI, TDI, performed on 26 exposed workers suggests an IgE-mediated sensitization, that does not appear to be a reliable diagnostic or prognostic factor of the disease.