[Decline in semen quality from 1930 to 1991]

It has been suspected for years that semen quality has declined. However, the issue is still controversial since previous studies were criticized for methodological errors. We therefore attempted to systematically review the complete international literature on semen quality since 1930 with rigorous selection criteria and statistical analysis. Based on a literature search using Cumulated Index Medicus and Current List (1930-1965) and MEDLINE Silver Platter database (1966-august 1991), we identified 61 papers concerning sperm density in a total of 14,957 males without a history of infertility. A significant decline in mean sperm density from 113 x 10(6)/ml in 1940 to 66 x 10(6)/ml in 1990 (p < 0.0001) and in mean seminal volume from 3.40 ml to 2.75 ml (p = 0.027) was noted. The incidence of testis cancer and possibly also that of cryptorchidism and hypospadias has increased during the same relatively short time period. Such a remarkable deterioration in male genitourinary function is more likely to be due to environmental rather than genetic factors.