We previously demonstrated in vitro that mammalian follicle-stimulating hormone (FSH) stimulates the proliferation of newt secondary spermatogonia and their differentiation into primary spermatocytes. In the current study, we isolated a cDNA from newt testis that encodes a FSH receptor (FSH-R). The total sequence homology in the deduced protein of the newt was approximately 70% with mammalian FSH-Rs. Mammalian cells, transiently transfected with the cloned newt FSH-R cDNA, displayed specific binding to [I-125] human FSK and cAMP accumulation, indicating that the cloned cDNA encodes a functional newt FSH-R protein. Northern blot analysis revealed a single transcript of approximately 3.0 kb length that was synthesized in testicular somatic cells (mainly Sertoli cells) from spermatogonial to spermatid stages with the highest level expressed during the primary spermatocytes stage. These results demonstrate that FSH stimulates newt spermatogenesis through the FSH-R. This study, as far as we know, reports for the first time the cloning of an amphibian FSH-R cDNA