Abstract We describe the cloning of HOXD1 in human unfertilised oocytes and detailed expression analyses during mouse oogenesis and embryogenesis. The cDNA of 1991 bp has an open reading frame of 987 bp encoding a protein of 329 amino acids. A comparison of the amino acid sequence with the mouse homologue revealed an overall homology of 85.5% with 99% identity within the homeodomain. Expression was detected in unfertilised human oocytes and 2-, 4-, 8-cell and blastocyst stage embryos. Expression analyses in mature mouse ovaries, early embryos and isolated gut revealed expression in the oocytes of the primary and secondary ovarian follicles, and in embryonal mesodermal derivatives such as dermatomes, urogenital tubercle, tail bud, kidney, ovaries, testes and enteric mesoderm adjacent to the caecum where expression was up-regulated in vitro in response to increasing doses of retinoic acid. Our observations indicate a possible role for HOXD1/ Hoxd1 in the ovarian oocytes and the establishment of mesodermal derivatives during embryogenesis.