Scientists at The Jackson Laboratory (TJL) have long seen the need to train a cadre of research scientists in the complexity of the genetic basis of immunological and hematological problems in intact animal model systems. This philosophy, an integral part of the Laboratory's Strategic Plan, has dictated the ongoing expansion of the overall training program at TJL. The Jackson Laboratory requests funding for continuation of its well-established postdoctoral research training program in immunology and hematology. Eleven members of the TJL Research Staff form an interdisciplinary pool of trainee preceptors who are investigating gene regulation and cell development in hemopoietic and lymphoid cell pathways in the mouse. Experimental work in these genetically-defined animal models provides the opportunity to test hypotheses regarding the genetic basis of immunological and hematological disorders and to model new diagnostic and therapeutic modalities. These types of analyses are made possible by the availability of the Laboratory's unparalleled resource base of special inbred, spontaneous and induced-mutant mice. TJL Postdoctoral program (4 trainees). Trainees devote their major effort to bench research, and are integrated into TJL seminars, courses, workshops, and research interest groups. They are required to write fellowship applications, and present their results both at in-house interest groups and international meetings. Their progress is overseen by a formal Training Committee, each member of which acts as an informal mentor, or liaison, for several trainees. Upon completion of training, participants will be qualified to engage in creative, independent research in hematology and immunology at a university, research institution, or in industry. The continued quality of the program is evidenced in part by the fact that all of the trainees supported by this grant in the last reporting period obtained independent fellowships. The primary training facility is TJL, a private, independent research center. TJL is an NIH Basic Cancer Research Center, raises 3 million mice annually, and has held NIH research training grants continuously since 1956.