Objectives: The aim of this study was to evaluate the coexisting factors and usefulness of diagnostic methods in metal-induced asthma in Polish welders. Materials and Methods: Examination of 50 welders occupationally exposed to metals and with suspicion of metal-induced asthma (group A), 100 welders occupationally exposed to metals but without suspicion of metal-induced asthma (group B), and two control groups (10 patients with atopic asthma and 10 healthy subjects) was carried out. Questionnaire survey, clinical examination, skin prick tests to common aeroallergens and metal salts, rest spirometry tests, X-ray, metacholine challenge and a single-blind, placebo controlled specific inhalation challenge tests with metals (or work-like conditions challenge tests) were performed. Results: In group A – in 9 cases we obtained positive results of specific inhalation challenge tests with metals (in 3 cases with nickel, in 4 cases with chromium, in 1 case with cobalt and in 1 case with manganese). Nine cases of metal-induced occupational asthma were recognized. In group B – only in one case we obtained positive results of work-like conditions challenge test (clinical and spirometry changes, eosinophil influx in induced sputum), which confirmed the diagnosis of occupational asthma. In most of examined welders (62%), pulmonary changes in chest X-ray images were noted. The statistical analysis revealed that working as a welder for more than 10 years is the coexisting factor of presence of chest X-ray changes (p- or q-type nodular changes or interstitial changes). Positive results of skin prick tests with metal salts were the coexisting factors of occupational asthma due to metals among examined group of welders. Conclusions: Specific inhalation challenge plays the key role in diagnostics of metal-induced asthma in welders. Pulmonary changes in chest X-ray were found in a significant percentage of examined welders.