The hCG/LH receptor belongs to the G-protein coupled receptor family. The gene for the receptor has been localised to chromosome 2p21. In addition to corpus luteum and testis as the classical target tissues for hCG and LH, hCG/LH receptors have been described in a variety of non-gonadal human tissues (e.g. endometrium, myometrium, fallopian tube, placenta, amnion, chorion, prostate, CNS, adrenal gland). Besides its modulation of endocrine functions, the hCG/LH receptor does probably transmit growth-factor like activities of hCG and LH in many of these tissues. Moreover, activating as well as inactivating mutations of the hCG/LH receptor gene have been described. These mutations are localised mainly within the transmembrane region of the receptor gene (exon 11) and are responsible for characteristic diseases such as familiar, male-limited precocious puberty as well as hypogonadism of both sexes. This review deals with the molecular biology of the hCG/LH receptor, its distribution within the human body, its functions as well as with the relevance of mutations. Finally, the therapeutic use of hCG in the treatment of AIDS-related Kaposis' sarcoma is discussed.