A case of professional asthma, following exposure to cefmetazole and 7-ACA, occurring in a non atopic subject with remarkable bronchial hyperreactivity, is described. From the diagnostic point of view the execution of specific bronchial stimulation tests was conclusive. It is probable that the occurrence of the illness is due, in this case, to the ability of the inhaled substances to cause inflammation in a subject with bronchial hyperreactivity, without inducing an immunologic mechanism.