This gene encodes an epididymal protease inhibitor, which contains both kunitz-type and WAP-type four-disulfide core (WFDC) protease inhibitor consensus sequences. Most WFDC genes are localized to chromosome 20q12-q13 in two clusters: centromeric and telomeric. This gene is a member of the WFDC gene family and belongs to the telomeric cluster. The protein can inhibit human sperm motility and exhibits antimicrobial activity against E. coli, and polymorphisms in this gene are associated with male infertility. Read-through transcription also exists between this gene and the downstream WFDC6 (WAP four-disulfide core domain 6) gene. Two transcript variants encoding different isoforms have been found for this gene.