A 53-year-old man, who had been exposed for 23 years to polyvinyl chloride (PVC) in the bagging area of a vinyl chloride polymerisation plant, presented with a diffuse micronodular infiltrate on his chest radiograph. Light microscopy of lung obtained by drill biopsy showed a diffuse infiltration with histiocytes and multinucleated giant cells, with some collagen formation. Ultrastructural studies showed foreign particles in the macrophages, which were identical with PVC powder viewed under the electron microscope. Incubation of PVC powder with human lung macrophages in vitro showed that the macrophages englufed the powder to give a similar ultrastructural appearance.