The prostate gland is an accessory sex organ of cloacal origin that contributes a number of enzymes to the seminal fluid, many aiding in seminal liquefaction after ejaculation. The prostate is located in the true pelvis and surrounds the urethra just distal to the bladder neck. The prostate is comprised of four distinct histological zones: central, peripheral, transitional, and the anterior fibromuscular stroma. The transitional zone is located adjacent to the urethra and is the smallest zone in the normal adult prostate. With age, however, the transitional zone often undergoes nodular hyperplastic changes and can cause significant enlargement, potentially leading to lower urinary tract symptoms (LUTS) and/or bladder outlet obstruction (BOO). Benign prostatic hyperplasia (BPH) is a term often used to describe the combination of prostatic enlargement and the resultant urinary symptoms. While nearly 70% of men experience prostatic enlargement by their seventh decade of life, the development of BPH is not altogether well-understood. Likely, a complex interplay of androgens and cell growth factors leads to the dysregulation of cellular growth inhibiting mechanisms, allowing for hypercellularity and enlargement of the transitional zone. The treatment of BPH requires a thorough understanding of normal prostate anatomy and physiology, as well as the pathophysiology of the disease process. This chapter will outline the normal development, anatomy, and physiology of the prostate, as well as the epidemiology, pathophysiology, and clinical features of BPH.