29 physicians (A1-Group) and 24 physicians (A2-Group) attending the 1st and 2nd "Asian Intensive Reader of Pneumoconiosis" (AIR Pneumo) training course, respectively, and 22 physicians (B-Group) attending the Brazilian training course took the examination of reading the 60-film set. The objective of the study was firstly to investigate the factor structure of physicians' proficiency of reading pneumoconiosis chest X-ray, and secondly to examine differences in factor scores between groups. Reading results in terms of the 8-index of all examinees (Examinee Group) were subjected to the exploratory factor analysis. A 4-factor was analyzed to structure the 8-index: the specificity for pneumoconiosis, specificity for large opacities, specificity for pleural plaque and shape differentiation for small opacities loaded on the Factor 1; the sensitivity for pneumoconiosis and sensitivity for large opacities loaded on the Factor 2; the sensitivity for pleural plaque loaded on the Factor 3; the profusion increment consistency loaded on the Factor 4. 4-Factor scores were compared between each other of the three groups. The Factor 2 scores in A1 and A2 groups were significantly higher than in B-Group. Four factors could reflect four aspects of reading proficiency of pneumoconiosis X-ray, and it was suggested that 4-factor scores could also assess the attained skills appropriately.