The objective of this study was to determine the usefulness of spirometry in the screening of chronic pulmonary problems related to exposure to welding fumes, in a regional public health-based screening program. Pulmonary questionnaires and spirometric tests were administered twice at 5-year intervals on 229 welders/cutters (mean age, 39.9 years from 31 metal manufacturing plants. The baseline mean value at the first test for the forced expiratory volume in one second (FEV1) was 102% of predicted, the forced vital capacity (FVC) was 107%, and the FEV1/FVC ratio was 79%. The mean annual changes in the three spirometric indicators were -47 mL, -46 mL, and -0.3%, respectively. The usefulness of spirometry was assessed by looking at the relationship between exposure to welding fumes and changes in spirometric indices, in multivariate linear regression analysis, accounting for age, height, and smoking. A high lifetime exposure to welding fumes was associated with better lung functions in the cross-sectional approach (healthy worker effect) but not in the longitudinal approach, where no association was found. We concluded that the public health regional application of this screening program generated too many sources of variation for spirometry to fulfill the objective of early detection of pulmonary function decline related to exposure to welding fumes. Based on these observations, we recommend that maintaining questionnaire screening, with spirometry reserved as a second-line diagnostic intervention.