Congenital bilateral absence of vas deferens: A condition in males when the tubes that carry sperm from the testes (the vas deferens) fail to develop normally. The testes usually develop and function normally and the men have normal sexual performance, but sperm cannot be transported through the male reproductive system. Men with congenital bilateral absence of vas deferens are therefore infertile (unable to conceive a child). This condition is responsible for 2 to 5% of all infertility in men.

Congenital bilateral absence of vas deferens is due to mutations in the CFTR gene (the cystic fibrosis transmembrane conductance regulator gene) which encodes a protein that functions as a channel across the cell membrane.