We report a case of occupational asthma caused by cobalt associated with systemic symptoms. He was a non-atopic, ex-smoker and had worked in a glassware factory for 14 months. A skin prick test with CoSO4 up to 100 mg/ml showed a negative result. A bronchoprovocation test with CoSO4 demonstrated an isolated asthmatic response with systemic symptoms such as fever, arthralgia and myalgia. Although an initial methacholine bronchial challenge test showed a negative result, the following methacholine bronchial challenge test which was done 24 hours after the challenge testing demonstrated an increased airway hyperresponsiveness at 2.5 mg/ml which recovered 7 days later. An intradermal skin test with 10 mg/ml and 100 mg/ml CoSO4 solution demonstrated positive responses respectively(13 x 12/40 x 32, 20 x 15/40 x 37 (mm), histamine 16 x 14/64 x 50). A patch test including cobalt showed a negative result. Bronchoalveolar lavage fluid after the cobalt inhalation testing and other laboratory findings showed no evidence of hypersensitivity pneumonitis. These results suggested that cobalt could induce occupational asthma with systemic illness in an exposed worker.