The phenotypic consequences of the defective CFTR function comprise insufficiency of the exocrine pancreas, increased electrolytes in sweat, male infertility due to congenital absence of the vas deferens, and—most prevalent—a debilitating progressive lung disease resulting from decreased mucociliary clearance with accumulation of thick, sticky mucus, chronic inflammation, and persistent and untreatable bacterial colonization causing frequent chest infections, mainly by Pseudomonas aeruginosa [1–3]. This evidence concerns the gene CFTR and male infertility.