Introduction: Semen analyses conducted on a sample of 26,609 men representative of the general population were used to analyze regional trends in sperm quality over time. The consistency of the observed results with regard to the potential role of environmental risk factors was examined. Method: Data were obtained from the Fivnat database, which recorded assisted reproductive technology (ART) attempts in mainland France during the study period (1989–2005). The selected men were partners of women who were completely infertile, undergoing their first attempt at ART using fresh semen. The three main indicators of sperm quality (concentration, total motility, and percentage of normal forms) were studied using an age-adjusted spatio-temporal Bayesian model. Results: The results show that sperm concentration and the percentage of normal forms have decreased in nearly all regions. Two regions, Aquitaine and Midi-Pyrénées, consistently exhibited more pronounced trends for these two indicators. Sperm motility increased slightly across all regions except Burgundy, which followed an opposite trend. Conclusion: A decline in sperm quality is observed in most metropolitan regions, suggesting the involvement of factors that have affected nearly the entire French population. This is consistent with the hypothesis of an effect of ubiquitous exposure to endocrine disruptors, with a possible local contribution from environmental exposure to pesticides in Aquitaine and Midi-Pyrénées. (R.A.)