A next-generation sequencing approach using a targeted PCD gene panel and WES in eight genetically undiagnosed males with suspected PCD and infertility revealed pathogenic variants in CCDC40, RSPH1, RSPH9, HYDIN, and SPEF2. In these individuals and two other males that were previously identified with pathogenic variants in CCDC39 and HYDIN (Merveille et al., 2011; Olbrich et al., 2012), further molecular and cell biological analyses were performed to characterize in more detail the composition and function of the axonemal ruler, RS and CP complex in sperm flagella. The gene discussed is HYDIN; the disease is Infertility.