PURPOSE: To describe the characteristic HRCT appearance and to evaluate the usefulness of HRCT in patients with welders' pneumoconiosis. MATERIALS AND METHODS: Chest radiographs and high-resolution computed tomography(HRCT) of 45 shipyard welders(male : female=41 : 4 ; age : 36-58 years, mean 47.8) with an occupational history of 4-25(mean 15.8) years were evaluated. Small rounded opacities in chest radiographs were read accordingto the ILO standard films(1980). HRCT were evaluated with micronodules, ground-glass attenuation, and other findings. Serial HRCT scans of seven welders taken 27 months apart were also evalauted. Two of these were still working in that job ; five had not worked as welders for 1-6(mean 4.4) years. RESULTS: HRCT of welders' pneumoconiosis showed poorly marginated centrilobular branching or dot opacities of low attenuation(n=36, 80.0%)with variable profusion and extent and ground-glass attenuation(n=8, 17.8%). HRCT abnormalities were seen in 39 welders(86.7%). It was able to depict micronodules(n=13) and/or ground-glass attenuation(n=3) in 15(68.2%) of 22welders with normal chest radiograph. Serial HRCT revealed no changes in parenchymal abnormalities(n=6) andslightly decreased profusion of micronodules(n=1). There was no HRCT abnormality suggesting gross parenchymal fibrosis. CONCLUSION: HRCT is more sensitive than chest radiography in detecting parenchymal changes in welders' pneumoconiosis, with characteristic poorly-marginated centrilobular branching opacities or dots and ground-glass attenuation. These HRCT appearances may be helpful in differentiating welders' pneumoconiosis from other diffuse lung diseases.