This chapter begins with intermediate mesoderm, and discusses the origin of the kidneys in human development, including the pronephros, mesonephros, and metanephros. It explains why the origin and development of the urinary and reproductive systems are considered together. The urinary and reproductive systems are considered together because of their close structural relationship in both time and space. The chapter describes the role of the sex chromosomes in human gender development, intermediate mesoderm, and the origin of the male and female reproductive ducts. The primary function of the ducts is to convey sperm from the seminiferous tubules, where they are formed, to the back of the vagina. The chapter explores the indifferent condition, the origin of the male and female sex glands, and also describes the development of the external genitalia of men and women. The female auxiliary sex glands are Skene's glands and Bartholin's glands, the functions of which are to provide lubrication at copulation.