Secretion of electrolytes and water by the epididymal epithelium is important in the formation an optimal fluid environment for sperm maturation and transport. This process is disrupted in the genetic disease cystic fibrosis caused by mutation of the cystic fibrosis transmemebrane conductance regulator (CFTR) gene. Recent findings of CFTR gene mutations in healthy men with congenital bilateral absence of the vas deferens or poor sperm quality may indicate that CFTR gene mutations have a far-reaching effect on human reproduction.