Six asthmatic subjects exposed to enzymatic detergents derived from B. Licheniformis were examined by means of a specific Bronchial Provocative Test (sBPT) with solutions of the enzyme. All subjects, except for one, were positive to prick tests with solutions of the "crude" enzyme and with Alcalase, and showed high levels of specific IgE by RAST. The sBPT with solutions of the enzyme, administered by means of a Bird Mark 7 nebulyzer in IPPB with measurement of the delivered dose, showed a positive response in all 6 subjects. No positive result was obtained in 5 normal subjects and in 5 non exposed asthmatic patients, even at much higher doses of the delivered enzyme. The occupational-type sBPT showed only two positive results out of the 6 examined. A good relationship was observed between bronchial hyperresponsiveness and provocative dose of the enzyme. Therefore, the sBPT with solutions of the enzyme is proved to be highly sensitive and specific in confirming the diagnosis of occupational asthma due to proteolytic enzymes.