Occupational asthma is one of the commonest occupational lung diseases. This is a case of asthma related to arc-welding in a shipyard. Serial peak expiratory flow rate readings were taken with and without exposure to the welding process. The results showed that the patient had occupational asthma from welding. This case report serves to remind us of the need to ask every adult with asthma for their occupational history. It emphasises the need for early diagnosis and removal from the cause of asthma. A delay in diagnosis may lead to non-specific bronchial reactivity and persistence of symptoms.