Objective: To review the literature on the association between male age and semen quality, fertility status and reproductive risks. Design: Review. Setting: Centre for infertility diagnosis and treatment Sanatorium Pronatal, Prague. Methods: Review of English language-published research over the last 20 years using MEDLINE. Results: The modification of gamete production in aging males is more qualitative than quantitative. However, aging of testes not only influences the individual, but through the gametes also offspring with increased risk of chromosomal, gene and behavioral abnormalities. Conclusion: It seems reasonable and consistent to recommend that both men and women complete their family before age 40 if possible.

        Key words: age, cytogenetics, fecundity, fertility, chromosomal aberrations, male infertility, mental functions, spermatogenesis