This document describes the background of test method EN 17181, its improvements compared to the existing standard test methods for measuring aerobic biodegradation of organic substances and the planning and execution of the interlaboratory study . A variety of data collected in the development of the method and the interlaboratory study is provided in this report, thereby supporting future activity associated with bio-lubricants and the definition of standard requirements. Aerobic biodegradation resulting in mineralisation of the organic material can be determined by measuring released CO2 using an appropriate analytical technique. EN 17181 specifies a procedure for determining the degree of aerobic degradation of organic material in fully formulated bio-lubricants. This organic material is exposed in a synthetic aqueous medium under laboratory conditions to an inoculum prepared from activated sludge. In contrast to existing test methods measuring released CO2 this new method uses a precise sample preparation procedure for poorly water-soluble organic material. Nevertheless, EN 17181 is also applicable to measuring the aerobic degradation of organic material present within fully formulated lubricants which are water-soluble or emulsifiable. NOTE In general, EN 17181 can be used to determine biodegradation of finished formulated lubricants, which contain biobased material of unknown amount or do not contain biobased material at all. All results and statistical data evaluation in this document are based on fresh water as test medium. Tests in sea water are currently not part of EN 17181.