Several engineering applications employing polymeric geosynthetic barriers need to have their tensile properties determined with confidence, according to standard test procedures that do not allow erroneous interpretations and decisions. However, there is no consensus on the standard test indicated to determine the tensile behavior of thin geomembranes in several recommendations and specifications in use. The paper compares the procedure adopted by American, International and Brazilian standards, and the results obtained in tests with PVC and fPP thin geomembranes. ABNT NBR 15826 and ISO 527-3 have the same procedure and present the most reliable results. ASTM D882 presents results closed with ISO results but with a lightly greater dispersion. ASTM D6693 presents a large dispersion of the results, and significant differences in percent elongation at break, with results 40% lower than ISO 527-3.