Aims: The aim of this study was to try to explain the pathogenesis of proximal hypospadias based on anatomical and histological findings. Methods: During 9 years, we performed systematic biopsies (in the lateral areas of the urethral plate, as well as under this plate) in 81 patients treated for proximal hypospadias. The histological study was performed by routine coloring, hematoxylin and eosin, and Masson's trichrome, which colors the collagen fibers in blue, and monoclonal antibody against alpha-smooth muscle actin. Results: There is a fibrosis tissue abnormally present on the ventral side of the penis. This tissue consists of a mixture of fibrous connective tissue, nerve nets, short vessels, and smooth muscle fibers. The penis' dartos does not contain smooth muscle fibers. These fibers can come from a blood vessel or spongy tissue which existed during the neonatal period in the distal part of the penis before disappearing. Conclusions: The proximal hypospadias is due presumably to avascular necrosis of the distal part poorly vascularized of the corpus spongiosum.