Scientists are currently in the midst of a genetics revolution that promises to push "breakthrough" biomedical research to new levels. A large part of this revolution depends upon the analysis of the relationships between genes and their effects on complex biological systems and phenotypes. Investigators must become increasingly skilled in the manipulation and use of genetic models to address a variety of important biological questions. The laboratory mouse has become the premier animal model for human and domestic animal diseases as well as the model of choice for studying basic biological functions. Establishing the validity of such models depends on interaction between molecular biologists, geneticists, and pathologists, all of which have overlapping, but distinct skills. This is especially true for the pathologists since most are trained as physicians who have little to no appreciation of interspecies variability and/or similarity. Likewise, veterinary pathologists, although used to working with many species, have little or no human pathology experience and often little or no mouse pathology expertise. The escalation in the production and use of genetically engineered mice has created a demand for individuals with mouse pathology expertise. Due to this severe deficit in pathologists with such expertise, the literature is being flooded with incomplete and inaccurate descriptions of phenotypic effects of mutated genes. In order to help address this problem, the investigators propose a workshop, "Pathology of the Laboratory Mouse," to be held in the Fall each year initially, for five years. The Jackson Laboratory will host the workshop in the odd-numbered years (one, three, and five) whereas Cornell and Purdue will alternately host the workshop in the even numbered years. Coupled with modest fees, these offsite options are intended to make the workshop more accessible to students. The workshop itself will consist of eight days of intensive bench training sessions in pathology and histopathology, as well as didactic sessions in which particular disease areas and models will be discussed. The Workshop will accommodate 16 participants who will have an opportunity to interact with a group of prominent mouse pathologists and geneticists from both TJL, and other leading institutions.