This proposal solicits continued support for diagnostic laboratories in service to the laboratory animal medicine program at the Yale School of Medicine. It will also support research directly related to elucidating diseases of laboratory animals and will support preliminary studies of potential animal models of human disease. Collaboration among the professional and technical staffs and combined utilization of facilities will be emphasized to achieve these objectives. Laboratories of anatomical pathology, clinical pathology (including clinical chemistry, hematology/cytology, microbiology) and virology will be maintained. Laboratory methods and services will be expanded and further refined in light of recent technical advances and to accommodate shifts in requirements of animal-related research at Yale. These laboratories have been in service for a number of years and utilize a broad spectrum of diagnostic methods. Additional emphasis will be put on development and evaluation of diagnostic tests for viral diseases and on the use of electron microscopy as a diagnostic and research technique for naturally-occurring diseases of laboratory animals.