Pathology standards for asbestos-associated diseases of the lungs and pleural cavities were recently developed by the Pneumoconiosis Committee of the United States College of American Pathologists under contract to the US National Institute for Occupational Safety and Health (NIOSH). The purpose of the contract was to develop standardized criteria for the pathological diagnosis of these diseases and to develop a system for grading the severity and extent of asbestosis. The results of a preliminary reading trial and the NIOSH statistical analysis of the trial are presented. These results indicate that the proposed grading schema has acceptable inter- and intra-observer variability. The variability is similar to that observed for radiologists in radiographic reading trials.