Seventy-five species and lower taxonomic units of rotifers have been identified in Lake Geneva (= lac Leman); seven species and one form are new for the lake. When using indicators of trophic conditions, the qualitative composition of the biocenosis is still dominated by oligo-mesotrophic lake indicators, mixed with eutrophic and oligotrophic ones. However the rotifer biocenosis has not yet reached a steady state.