This article traces the evolution of approaches to the diagnosis and treatment of erectile dysfunction (ED) throughout the 20th century — from the early dominance of psychiatry in this field (the concepts of Sigmund Freud and the couples‑based sex‑therapy methodology of Masters and Johnson) to the establishment of urology as the leading discipline in the study of male sexual disorders. The article reviews the history of research on nocturnal erections and their role in the differential diagnosis of psychogenic and organic forms of ED. Particular attention is paid to the revolutionary contributions of Tom Lue and Irwin Goldstein to the development of evidence‑based erectile physiology, ED pharmacotherapy, and the recognition of ED as an early marker of systemic vascular disease. At the same time, the author outlines the main results of his own 1980s investigations, including the development of selective arteriography and dynamic cavernosography, the formulation of postulates on vascular, neurogenic, and endocrine mechanisms of ED, as well as clinical experience with implant surgery in 200 patients. It is emphasized that the 1970s–1980s were a period of fundamental discoveries that laid the foundation for modern diagnostic and therapeutic strategies in ED.