Bilateral seminal duct obstruction leads to azoospermia and male infertility. In men with unilateral obstruction fertility may be unaffected or may be heavy impaired because of a reduced sperm cells number in the semen. Causes of seminal ducts obstruction may be genetic (cystic fibrosis, aplasia of the vas deferens), congenital (malformations of the prostate gland) or acquired (post inflammatory changes in the epididymis, prostate, vasectomy, inguinal hernia repair). Diagnosis of duct obstruction is made after semen analysis, seminal plasma biochemical tests (fructose and citric acid concentration, neutral α‑glucosidase activity), genetics test, imaging or diagnostics of infection. Obstruction treatment depends on the cause and may involve the use of assisted reproduction techniques, surgical restoration of ducts patency or infection therapy.