Del Castillo, Trabucco and De la Balze syndrome was described in five patients in Buenos Aires in 1947. Secondary sexual characteristics and urological examination were normal, except for small testicle volume (“the size of an olive”). Treatment with hCG was ineffective. On testicular biopsy, only Sertoli cells and seminiferous tubules were detected, with no spermatozoa or spermatogonia. For this reason, it is currently known as testicular germ cell aplasia or Sertoli cell-only syndrome (SCOS). SCOS is the most severe histological phenotype of male infertility, associated with non-obstructive azoospermia and low testicular volume. This review provides a comprehensive synthesis of the historical background, clinical presentation, hormonal and histological features, genetic underpinnings and emerging therapeutic perspectives in SCOS.