Certain adverse trends in male reproductive health were noted by researchers in the late 1900s demonstrating declining semen quality. At the same time, the incidence of testis cancer, cryptorchidism, and hypospadias increased in the same geographic areas. Looking for a common underlying explanation, the theory of a testicular dysgenesis syndrome was coined, describing how a disturbance in the development of the male urogenital tract in fetal life, partly due to in utero exposure to endocrine disruptors, can have consequences including birth defects such as cryptorchidism and hypospadias and long-term clinical conditions such as testis cancer and male infertility. While the associations between these conditions have been established, the theory still has limitations. Much of the evidence gathered stems from animal studies and observational studies, and causation in humans with interventional studies exposing pregnant women to endocrine disruptors is, of course, impossible to perform. However, the sum of today’s evidence points to a detrimental role of exposure to endocrine disruptors possibly causing testicular dysgenesis with impact on men’s health.