A partial estrogen receptor beta (ER-β) cDNA was isolated from testicular quail RNA by RT-PCR with degenerate primers specific to the rat ER-β sequence. A high expression of ER-β was demonstrated by RT-PCR in the telencephalon, diencephalon, pituitary, testis and kidneys of male quail but little or no expression was detected in the cerebellum, pectoral muscle and adrenal gland.In situhybridization with a35S-labelled oligoprobe in sections through the preoptic area-rostral hypothalamus identified high expression in the medial preoptic nucleus, bed nucleus striae terminalis and nucleus taeniae. These data demonstrate the presence of an ER-β in brain areas implicated in the control of reproduction in a non-mammalian species.