In humans androgen decline is presented as a clinical picture which includes decreased sexual interest, diminished erectile capacity, delayed or absent orgasms and reduced sexual pleasure. Additionally, changes in mood, diminished well being, fatigue, depression and irritability are also associated with androgen insufficiency. The critical role of androgens on the development, growth, and maintenance of the penis has been widely accepted. Although, the exact effect of androgens on erectile physiology still remains undetermined, recent experimental studies have broaden our understanding about the relationship between androgens and erectile function. Preclinical studies showed that androgen deprivation leads to penile tissue atrophy and alterations in the nerve structures of the penis. Furthermore, androgen deprivation caused to accumulation of fat containing cells and decreased protein expression of endothelial and neuronal nitric oxide synthases (eNOS and nNOS), and phosphodiesterase type-5 (PDE-5), which play crucial role in normal erectile physiology. On the light of the recent literature, we aimed to present the direct effect of androgens on the structures, development and maintenance of penile tissue and erectile physiology as well. Furthermore, according to the clinical studies we conclude the aetiology, pathophysiology, prevalence, diagnosis and treatment options of hypogonadism in aging men.