Introduction - A decline in sperm concentration has been observed worldwide and in certain regions of France for periods prior to 1994. In utero exposure to endocrine disruptors is suspected of contributing to male reproductive disorders, including reduced sperm quality. To assess the current situation, we conducted a retrospective study on trends in sperm concentration in mainland France between 1989 and 2005, using the Fivnat database. Materials and Methods - We analyzed trends in sperm concentration among men in couples undergoing their first attempt at assisted reproductive technology, as well as in two subsamples: one representative of the general population and the other of fertile men. We used a nonlinear model, adjusted for age, technique, and season when the date was available. We included the interaction between time and technique. Results - The trends observed for men who underwent IVF were similar across all three populations, showing a three-phase pattern: a decline from 1989 to 1994 (phase 1), an increase from 1995 to 2000 (phase 2), and a decline from 2001 to 2005 (phase 3). Discussion - Conclusion - The declines in phases 1 and 3 suggest a real decrease in sperm concentration during these periods. And the possibility of a decline in phase 2, possibly masked by advances in techniques, cannot be ruled out. These preliminary results, which should be interpreted with caution, will need to be supplemented by monitoring other indicators of sperm quality (motility, morphology). (R.A.)