The genetic distances between several strains of Senedesmus obliquus (Turp,) Kutz,, S, acutus Hortobagyi, and S, naegelii Chod. calculated from ITS-2 sequences were found to be smaller than the genetic distances within other strains of Scenedesmus-that is, in S, acuminatus (Lagerh,) Chod, and S, pectinatus Meyen. These results confirm that the studied strains were not properly identified and should be renamed S, obliquus, as already suggested in other studies. [KEYWORDS: ITS, phylogeny, Scenedesmus acutus, Scenedesmus naegelii, Scenedesmus obliquus]