Species composition of microscopic algae of the Odesa filtration fields was studied.The Odesa filtration fields have acted as purifying constructions of the local sewage system since 1888. During quite a long time period purification of sewage waters has been successfully combined with their agricultural application on the filtration fields. Now the area of the Odesa filtration fields constitutes 630 ha.Algae of the Odesa filtration fields take active part in purification of sewage waters from pollution, production of oxygen and silt. In addition, they are used as indicator organisms of salinity, pH and organic contamination of water.Algoflora of the Odesa filtration fields practically has not been studied, some literature data (Gerasimiuk, 1094; Gusliakov, Zakordonets, Gerasimiuk, 1992) are known only about diatoms, other phyla of algae have not been given appropriate attention.The aim of the work is to study the modern condition of species composition of the algae from the study area. Microscopic algae were studied in plankton, fouling with microphytes (Cladophora glomerata (L.) Kutz., Enteromorpha flexuosa (Wulf.) J. Agardh, Lemna trisulca L., Phragmites australis, Potamogeton pectinatus L., Rhizoclonium implexum (Dillw.) Kutz., Spirogyra decimina (Mull.) Kutz., Typha angustifolia L., Ulothrix tenerrima (Kutz.) Kutz.), in slimy film of loose soils (silt and sand), as well as in glass fouling. Sampling was carried out in accordance with universally accepted methods. During 2011-2012 69 species of algae, belonging to 5 phyla: Bacillariophyta (59 видів), Cyanophyta (6), Chlorophyta (2), Euglenophyta (1), Streptophyta (1) were identified at 8 stations of the said water reservoirs. 58 species of microphytes of them were found for the first time.