Abstract : Observations from space of the open water areas within Lake Chad are presented. They complement and sustain the earlier study of Mohler et al. (1989), which demonstrates a decrease of about 90 percent in surface between 1966 and 1986. Further, Meteosat images were processed to obtain weekly maps of albedo following the scheme of Moussu et al. (1989). The analysis of these maps throughout the year reveals the functioning of the lake as well as the large variability of the open water areas during a year.