Screening of a human genomic library with a cDNA probe corresponding to the transmembrane domain of the FSH receptor (FSHR) resulted in the identification of a positive clone with a DNA insert of approximately 17·5 kb. Part of the clone encoded exon 10 of the FSHR gene. Sequence analysis of this exon revealed an open reading frame corresponding to base positions 855–2085 of the FSHR cDNA, thereby coding for 410 amino acids. Exon 10 was found to comprise the seven transmembrane domains, the C-terminal intracellular domain and a fragment of 81 amino acids belonging to the extracellular N-terminal domain of the FSHR. The exon/intron boundary is in phase 2 and the amino acid which resides in this junction is isoleucine. The genomic clone was used to map the chromosomal localization of the human FSHR gene. In situ hybridization experiments allowed the allocation of the human gene to chromosome 2 p21. As this position is identical to that of the human LH receptor gene, these two receptor genes may have evolved from a common ancestor.