The prostate is a male accessory sex gland found only in mammals that functions to produce a major fraction of seminal fluid. Interest in understanding the biology of the prostate is driven both by the fascinating nature of the developmental processes that give rise to the prostate and by the high incidence in humans of prostatic diseases, including prostatic adenocarcinoma and benign prostatic hyperplasia. This review summarizes the current state of knowledge of the cellular and molecular processes that control prostatic development. Insight into the mechanisms that control prostatic development has come from experimental embryological work as well as from the study of mice and humans harboring mutations that alter prostatic development. These studies have demonstrated a requirement for androgens throughout prostatic development and have revealed a series of reciprocal paracrine signals between the developing prostatic epithelium and prostatic mesenchyme. Finally, these studies have identified several specific gene products that are required for prostatic development. While research in recent years has greatly enhanced our understanding of the molecular control of prostatic development, known genes cannot yet explain in molecular terms the complex biological interactions that descriptive and experimental embryological studies have elucidated in the control of prostatic development.