Biotic and the abiotic degradabilities of organic chemicals are largely influenced by the potential exposure of substances to organisms and, hence, are key parameters in risk assessment for predicting spatio-temporal environmental concentrations and long-term adverse effects. Degradability in particular could be a bottleneck in designing inherently safer and sustainable ILs, because the tendency of certain ILs to be thermally and chemically very stable is often reflected by their great vis-a-vis biological degradation processes. The following review article will provide an introduction to biodegradation test procedures and will present an overview of existing aerobic and anaerobic IL biodegradation data. The discussion of this data should help to improve the future design of inherently safer ILs, thereby reducing the risks they may pose to humans and the environment.