The prevalence of pneumoconioses among phosphate (1306054) rock workers in Brazil was assessed. The 73 workers evaluated in the investigation were exposed to phosphate rock extracted in the states of Goias and Minas Gerais, where the material was crushed and then transported to Paulinia for storage in underground mills. Subjects submitted to a detailed respiratory questionnaire, a physical examination emphasizing the respiratory system, pulmonary function tests, chest x-rays, and, in two cases, lung biopsies through thoracotomy. The quantity of free silica (7631869) in airborne samples was measured by colorimetric analysis. A semiquantitative analysis was performed on airborne samples using x-ray spectrometry. Twenty of the workers were noted to have pneumoconioses. Mean exposure was 46 months. The majority of the cases had no respiratory symptoms. No significant fibrosis was noted, and no pleura disease or mediastinal alterations were observed. No traces of free silica were detected by diffraction analysis. The author concludes that the high prevalence of pneumoconioses noted in this study must derive from the particularly poor working conditions at the facilities. A regular followup using lung function tests and chest x-rays should be included in the routine examination of phosphate rock workers.