Gonadotropins consist of two types of glycoprotein hormone: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones are heterodimers composed of a common alpha subunit and unique beta subunits encoded by genes localized on different chromosomes and synthesized in the same type of anterior pituitary cells. It is known that the expressions of these three subunit genes are regulated differently, by several extracellular factors. Determination of the DNA sequences of the genes has demonstrated that several potential regulatory sequences are present, and some of these sequences have been surveyed by transient expression experiments of the chimeric gene fragments. However, these studies have provided only limited information, and the trans-acting factors are still unclear. Recently, transgenic technology has provided some interesting information on the tissue- and cell-specific expression of the gonadotropin subunits and their hormonal regulation. This line of investigation must be expanded to provide a complete understanding of the regulatory mechanism of gonadotropin gene expression at the molecular level.