Dr. Harold Hafs's impact on animal agriculture and the American Society of Animal Science during his 45-year career is meritorious. Hafs's research has focused on methods to enhance and control reproduction in domestic animals. He was a pioneer in developing techniques to freeze sperm and synchronize estrus, and he is an authority on prostaglandins and the control of anterior pituitary hormone secretion. Hafs has worked extensively in pituitary and hypothalamic control of reproduction, and he was a major contributor to our knowledge of reproductive development and the onset of puberty in males and females. Harold Hafs's service to the livestock industry has been as exemplary as his research. He has accepted professional responsibilities within ASAS, ADSA, and SSR, and he was a founding member of the board of trustees of the ASAS Foundation. Hafs has also brought his scientific expertise to NIH, FDA, and USDA. He has provided leadership in the animal sciences in both academia and industry by serving as chair of the Department of Dairy Science at Michigan State University, vice-president for animal science research and development at Merck, and, most recently, as the chair of Animal Sciences at Rutgers. Throughout his career, Hafs readily accepted the responsibility of training and mentoring young scientists. He has personally trained numerous students, and he has assisted the careers of many faculty at institutions across the country. His published views on graduate training have helped shape our present system.