The biogeological evolution of Nador lagoon over the 1982-1993 period was surveyed through water parameters, chlorophyll biomass, macrobenthos and surficial sediments. Comparison of present data with the 1982-83 ones (Guelorget et al., 1984) shows that: the general organization and functioning of the basin (water circulation, biological and sedimentological zonations) remain roughly the same, the global confinement as described by the biological zonation has slightly increased, with an extension of the high confinement zones (zones IV to VI) to the detriment of the low confinement zones, notably zones I and II, the main change has been eutrophication and a dramatic increase elf organic matter inputs and sedimentation, due to increasing urbanization and the development of aquacultural activities. This evolution seems to be irreversible. Beyond these environmental considerations, this study also permitted a clearer definition of the relationships between the basin and the sea.