Introduction: Polygonum aviculare L. (Polygonaceae) is an annual plant. There are about 300 species of genus Polygonum. Polygonum aviculare is a weed plant which is widely spread in Russia and the Ukraine. All the aerial parts of plant can be used as a medicinal plant raw material. It is extensively used in traditional and official medicine for treatment of urinary diseases [1].The aim of this work is to make Pharmacognostic analysis of Herba Polygoni avicularis and to identify the main biologically active substances. To achieve this goal we should make the following tasks: 1) to do macro- and microscopic analysis; 2) to make phytochemical analysis; 3) to identify a quantitative determination of the sum of flavonoids according to the State Pharmacopoeia of the USSR. Ed. XI (part 2).As a plant raw material in this research we used HerbaPolygoni avicularis of “LEK+” firm manufacturing.During the work we found out the concordance of “general appearance” according to the macroscopic analysis, as there were pieces of caulis, leaves, blooms of different shapes with greenish-grey colour and faint odour. Also, during the microscopic analysis we identified the main anatomical diagnostic features which are straight cells on epidermis with thickened walls and brown contents, numerous crystals of calcium oxalate in mesophyll, the presence of mechanical fibers with curving outlines and thickened layers [2]. Moreover, we made purity tests and identifiedquantitative determination of flavonoids. The results: sum of flavonoids calculated as avicularin – 5,2% (should be not less than 0,5 %) by spectrophotometry (λ=410 nm); loss on drying (where we dried our raw material (t=1070C) in a drying closet, weighed up and calculated) - 12% (not more than 13%); total ash (we burned out organics in an ash muffle) – 5,8% (not more than 13%), foreign organic matter – 0,3 % (not more than 2%) and mineral impurity – 0,5% (not more than 2%) [2]. We identified the presence of flavonoids, tannins, polysaccharides and saponins using standard identity tests [3].In general, during the Pharmacognostic analysis of Herba Polygoni avicularis we set up the correspondence of main characteristics to the general pharmacopeial monograph. We identified the presence of flavonoids, tannins, polysaccharides and saponins.References:1. http://medicalherbs.sci-lib.com/herbs042.html2. State Pharmacopoeia of the USSR. Ed. XI (part 2). Common methods of analysis. Medical plant material / USSR Ministry of Health. - 11th ed., Ext.– M.: Medicine, 1990. - 400 p.3. Grinkevich N.I., Safronich L.N. Chemical analysis of medical plants. – M.: Higher school