These hearings before the House of Representatives Committee on Government Reform address possible reasons for the apparently rapid increase in the incidence of autism. An introduction by the Committee Chairman, Dan Burton, provides background information and suggests a possible linkage between autism and the mumps-measles-rubella vaccine, specifically the possibility of mercury contamination. Text is included of statements from representatives of the following: the Committee on Immunization Safety, Institute of Medicine; National Academy of Sciences; Indiana University School of Medicine; McGill University; MIND Institute, University of California, Davis; National Institute of Child Health and Human Development; Office of Vaccine Research and Review, Food and Drug Administration; Office of Vital Statistics and Epidemiology; and the Center on Birth Defects and Developmental Disabilities. Extensive letters, statements, and other materials are also included. (DB)