Members of the ADAM (A Disintegrin And Metalloprotease) family of cell surface proteins have been discovered in a variety of tissues and species. We have cloned and sequenced a mouse cDNA encoding a novel member of the ADAM family. This mouse ADAM gene was named ADAM32 after an human homologue previously sequenced but not characterized. The cDNA sequence of ADAM32 has an open reading frame which encodes 750 (mouse ADAM32) and 787 (human ADAM32) amino acids, sharing 69% homology between the two species. The deduced amino acid sequences of mouse and human ADAM32 cDNAs contain all of the domains common to ADAM family members. Comparison of amino acid sequences showed that ADAM32 is highly homologous to ADAM2 and ADAM3, sperm surface proteins required for fertilization. We found that the ADAM32 gene is expressed predominantly in the testis. Examination of transcription in pre-pubertal and adult mouse testes revealed that expression of ADAM32 begins during meiotic prophase, in pachytene spermatocytes. These results suggest a potential role for ADAM32 in sperm development or fertilization. Genome database searches revealed that the mouse and human ADAM32 genes are located on chromosomes 8 and 8q11, respectively. The ADAM32 gene covers a relatively large region of the genome (120 kb for mouse ADAM32 and 180 kb for human ADAM32) and consists of multiple small exons (at least 22 exons in mouse ADAM32 and 25 exons in human ADAM32).