7-ACA(7-aminocephalosporanic acid) and ACT(aminocephalosporanic thiazine) are basic materials for development of 2nd and 3rd generation cephalosporin. Occupational asthmas(OA) induced by these materials have been very rarely reported. We had experienced 2 cases of OA by them. One was 26 year-old male laboratorian involving 7ACA manufacturing directly. The other case was 40 year-old male asthmatics working at the ware house keeping 7ACA and ACT, not directly making these. The result of skin prick test with 55 common inhalant allergens and 7ACA, ACT and several cephalosporins including Cefazolin, Cefuroxime, Ceftazidime, Cefotaxime, Ceftriaxone and Cefotetan. First case revealed positive reactions to 7ACA and Ceftriaxone, but second case, only positive to ACT. In first case, bronchial challenge with 7ACA only showed positive, but in second, those with 7ACA and ACT both showed positive, though negative to 7ACA in skin test.