The chromosome complement of the freshwater mussel Anodonta anatina was studied using Giemsa, Ag-NOR and chromomycin A3 staining. The diploid chromosome number of this species is 2n=38 and the arm number (NF) = 76. The nucleolar organizer region (NOR) was found on one chromosome pair and it was connected to GC rich chromatin as visualized by CMA3 staining.