This paper presents the results of an experimental study aiming at evaluating the performance of two different bituminous geomembranes, an elastomeric bituminous geomembrane and an oxidized bituminous geomembranes, installed in two parts of the same pond, in France, after 15 years in service. A presentation of the difference between elastomeric and oxidized bitumen is first given to clarify the differences existing between the two varieties of bitumen used in the manufacturing of geomembranes, resulting in different properties. Results of the visual inspection of the geomembrane, of flow rate measurement and size exclusion chromatography tests are then presented. In the case reported here the oxidized bituminous geomembrane performance is less by one order of magnitude than that of the elastomeric bituminous geomembrane in relation with bitumen embrittlement.