Summary

• Presence of abnormal semen parameters in the male partner of a couple unable to achieve conception after 1 year of unprotected intercourse.
• Male factor alone contributes to 20% of cases of infertile couples and to an additional 30% to 40% in combination with other factors.
• Most cases are of unknown aetiology.
• Diagnosed if abnormal semen parameters in 2 semen analyses separated by 1 month.
• Sperm functional assays, endocrine tests, genetic testing, and imaging can be helpful.
• Treatment should be targeted to the aetiological factors whenever possible.
• Assisted reproductive techniques are often the fastest and most effective method to achieve pregnancy regardless of the aetiology.