The metalloproteinase-like, disintegrin-like, cysteine-rich (MDC) family is a large group of sequence-related proteins, first characterized in the male reproductive tract, but subsequently also identified in non-reproductive tissues. Their primary translation products are of approximately 90 kDa and each can be divided into distinct domains which show remarkable homology to reprolysins; snake venom haemorrhagic components possessing metalloproteinase and/or disintegrin domains. Several MDC proteins are abundantly-expressed in the male reproductive tract, suggesting functions in fertility. We now describe the cloning, sequence determination and characterization of transcripts encoding the human and macaque (Macaca fascicularis) orthologues of a novel member of the MDC family (eMDC II) which is abundantly-expressed in the epididymis. Unlike many MDC proteins expressed in the reproductive tract, eMDC II possesses the extended 'catalytic centre' consensus sequence characteristic of a reprolysin-like metalloproteinase. This suggests that eMDC II has proteolytic activity.