WHO laboratory manual for the examination and processing of human semen Fifth editionSemen analysis may be useful in both clinical and research settings, for investigating male fertility status as well as monitoring spermatogenesis during and following male fertility regulation and other interventions. This manual provides updated, standardized, evidence-based procedures and recommendations for laboratory managers, scientists and technicians to follow in examining human semen in a clinical or research setting. Detailed protocols for routine, optional and research tests are elaborated.