Ethyl sulfate (EtS) is a non-oxidative metabolite of ethanol, used for forensic purposes as an ethanol consumption marker in addition to the ethanol metabolite ethyl glucuronide (EtG) which after certain scientific publications is prone to biological degradation. As ethanol is widely consumed in many western cultures, knowledge about the stability of ethyl sulfate against biodegradation is of importance for forensic investigations-where EtS until now was thought to be stable against bacterial degradation. Using standardized test methods from the panel of OECD tests, the stability of EtS against bacterial degradation was assessed in this study. These experiments showed that EtS was stable in the closed bottle test (CBT) (OECD 301 D), but not in the manometric respiratory test (MRT) (OECD 301 F) with higher bacterial density. With respect to forensic investigations the assumption of EtS stability could be disproved and the possibility of bacterial degradation of EtS should be taken into account when alcohol uptake some hours prior to death needs to be ruled out by determination of alcohol consumption markers in putrefied corpses, where ethanol concentration could have been generated post-mortem by fermentation processes. © 2009 Elsevier Ireland Ltd. All rights reserved.