This application seeks a third Competitive Renewal of application T32 AR007605 "Genetic Mechanisms in Skin Diseases" for continued funding of an established training program in Investigative Dermatology at Columbia University, College of Physicians &Surgeons. The Program has been extraordinarily successful in the last award period, having recruited 11outstanding trainees of diverse backgrounds. Six of the eleven trainees (55%) were women, four of the eleven (36%) were underrepresented minorities, and 3 of the eleven (27%) were MDs training to be physician-scientists, while the remaining 8 were PhDs All trainees have published papers, presented abstracts as posters and given oral presentations at prominent meetings, and all have stayed either in academia, the biopharmaceutical/technology industry, or have furthered their careers in medicine by going on to residency training. In this renewal, we request positions for four postdoctoral trainees, for a training program consisting of twenty-three outstanding trainers. Our goal is to train independent investigators capable of designing and executing programs of excellence in dermatological research. This program rests on a foundation of well-funded research in the biology of the skin and its diseases within the Department of Dermatology which totals over $4,000,000 of annual direct cost funds from the National Institutes of Health. The training program has two Specific Aims: first, to give trainees a broad perspective of current knowledge and the major questions facing investigative dermatology;second to offer a wide choice of research training opportunities in investigative dermatology, using a variety of model systems that will allow the development of a hypothesis-driven, mechanistically oriented research program tailored to the individual trainee. Research areas available to trainees include but are not limited to: mechanisms of carcinogenesis, the molecular basis of inherited skin and hair disorders, stem cells, control of hair follicle cycling, chemoprevention of skin cancer, cell cycle control, and pigmentation. Trainees are rigorously selected by a Selection and Steering Committee on the basis of academic excellence, investigative ability, and commitment to a career in investigative dermatology. Importantly, the research training experience of chosen candidates requires instruction in the Responsible Conduct of Research, a workshop in grantsmanship, as well as written and oral presentation of their work at local and national meetings. We will continue to capitalize on the strengths of the funded investigators in the Department of Dermatology, as well as the outstanding trainers we have recruited from the University community, to provide trainees with a unique mentorship experience that has an outstanding ten-year track-record of fostering careers in investigative dermatology.