The term hamartoma was coined by Albrecht in 1904 from the Greek mart-ánv, to go wrong [1]. Hamartoma is currently used to name nonneoplastic lesions composed of disorganized tissue indigenous to the site where it is found. In the testis, this refers to abnormal/excessive development of structures that usually form part of the gonadal parenchyma, epididymis, or spermatic cord. We include the following as hamartomatous lesions of the testis and sperm excretory ducts: cystic dysplasia of the rete testis, rete testis hamartomas, fetal gonadoblastoid testicular dysplasia (FGTD), Sertoli cell nodules, tubular hamartomas, congenital testicular and epididymal lymphangiectasis, and smooth muscle hyperplasia of paratesticular structures. These hamartomas are always benign, but their importance resides in their association with specific disorders, or as markers of complex syndromes.