This R13 conference grant application requests funds to support the XXIst North American Testis Workshop (NATW) to be held at the Hyatt Regency Montreal March 30 - April 2, 2011. This conference, first held in 1972, has established a tradition as an outstanding investigator-initiated meeting bringing together leading basic and clinical scientists in the field of testis biology. It is viewed as an essential conference for trainees in the field with graduate students, MD/PhD students, and postdoctoral fellows making up nearly half of the attendees. It is also viewed as a 'must attend' meeting for senior investigators active in areas of research involving the testis or testicular cells, as it is known to feature the most current research in these areas. The NATW is held every two years, immediately prior to the annual meeting of the American Society of Andrology at the same venue. Thus, this meeting provides a significant contribution to the progress of research relevant to male reproductive health. Scientists from beyond the United States and Canada also participate actively as attendees, speakers, members of the Program Organizing Committee, and poster presenters. Leading investigators in the field are featured on the program, interspersed with short talks selected from submitted abstracts, the majority of which are presented by trainees or junior faculty. The theme of the XXIst NATW will be "Testicular Determinants of Reproductive Success." There will be a keynote session on the opening night, followed by five scientific sessions over the next two and one half days. A total of 20 invited speakers have been confirmed for the five scientific sessions. The Keynote Address will be presented by Dr. Azim Surani from the Gurdon Institute in the UK and will be entitled, "Germ Cells: The Eternal Link between All Generations." The topics of the five scientific sessions will be "Origins of the Testis and Spermatogenic Cells," "Meiotic Events - Reproductive and Clinical Ramifications," "Programming and Packaging the Paternal Genome," "Regulation of Testis Function," and "Environmental Impacts on Testicular Function." Each session will feature four invited speakers, plus two short talks to be selected from submitted abstracts. Finally, there will also be two poster sessions so that every attendee who wishes to do so will have an opportunity to present their work. Funds are requested to support travel and lodging costs for a subset of the invited speakers plus to provide travel awards to 10 trainees whose abstracts are selected to be presented as short talks during the plenary sessions. PUBLIC HEALTH RELEVANCE: Infertility is a problem that affects approximately 12% of couples in developed countries including the United States and Canada, and male-factor or idiopathic infertility is responsible for approximately two thirds of these conditions. The North American Testis Workshop (NATW) is the only conference dedicated to basic and clinical studies of testis function and clinical ramifications. The theme of this workshop will be "Testicular Determinants of Reproductive Success." The XXIst NATW will continue a well-established heritage by covering cutting-edge research presented by world-leaders, as well as by fostering the inclusion and career development of trainees, women, underrepresented minorities and individuals with disabilities.