Dr. Patrick Walsh's description of nerve-sparing prostatectomy was an important landmark in the surgical treatment of prostate cancer. Despite the dramatic improvement in postoperative potency rates, anecdotal reports of penile size loss were increasingly reported by patients. Experimental studies in animals revealed penile fibrosis and corporal cavernosal smooth muscle apoptosis after cavernosal nerve ablation. After an observational cross-sectional study demonstrated a time-dependent loss of penile length and circumference in men presenting with erectile dysfunction after nerve-sparing prostatectomy, several prospective studies supported the observational study. A prospective penile biopsy study before and after surgery demonstrated replacement of corporal smooth muscle with collagen and provided a possible explanation for loss of penile length. The mechanism has not yet been elucidated. This article reviews in detail the existing studies on loss of penile size after prostatectomy and possible etiologic mechanisms.