Bodily waste became central to scientific research and practice after World War I. Taking urine as its main substance, and infertility as a central problem, the project looks at this unexplored process. I examine the development of sex endocrinology, and the ways in which urine became the field's leading resource and research material. More specifically, I ask how human, equine, and bovine urine was turned from waste into a promising fertility drug. The project pays particular attention to a circle of European gynecologists, agriculturists, and hormone researchers who settled in Palestine in the 1930s, and attempted to find solutions to fertility problems among settlers and their animals. As a result of such efforts to overcome infertility, urine connected human and animal bodies, and scientific institutions to the booming pharmaceutical industry. Its flows offered a solution to the limitations of the body, but at the same time, posed a threat to the integrity of bodies, and to the status of the scientists who worked with them.