In congener analysis different sample preparation techniques and varying methods of headspace analysis and chromatography are used. In addition, biological material, which can be rather difficult to handle, is analysed. Nevertheless, results of proficiency tests proved congener analysis to be a very reliable technique for the investigation of relevant analytics also in conjunction with different methods and defined analytical criteria. The association 'Alcohol Consumption and After Drinking' is soon to lay down guidelines for carrying out these analyses taking the results of this work into consideration.