A combination of rheumatoid arthritis and pneumoconiosis is observed in 2-6% of cases of diseases among people occupationally exposed to either the crystal or fibrous form of silica. Chest radiology of patients affected by this syndrome shows multiple, rounded opacifications, usually 0.5-5.0 cm in diameter, as well as positive serologic reactions to the presence of the rheumatoid agent. The authors analysed a comprehensive material of 187 cases with the diagnosis of pneumoconiosis in grinders/casting cleaners with an homogenous source of exposure to fibrous dust, and one observed case of Caplan’s syndrome in a female who worked as a crane operator. The diagnosis was made based on occupational interview, evaluation of X-ray of the chest and bones, and serologic response typical for rheumatoid arthritis. Pneumoconiosis preceded rheumatoid arthritis by several years. Within 7 years of ambulatory follow-up, the progression of radiological changes in the lungs remained moderate, both with respect to type and density of the opacities.