The first ADVOCATE network summer school on the theme of Assessment of contaminant source identification, natural processes and remediation performance using stable isotopes, with field sampling and laboratory analysis was hosted at the UFZ Leipzig, Germany, on 21/22 June 2012. This event was attended by 23 fellows and external participants, who included researchers and professional environmental engineers from Europe. Over the two days the participants were introduced to the fundamental theory and application of stable isotope analysis for the evaluation of contaminant sources, biodegradation processes and in situ remediation performance. Particular emphasis was given to the integration of this analysis with other multidisciplinary techniques to develop a comprehensive understanding of the environmental fate of organic chemicals in the subsurface. The school included a visit to the isotope geochemistry laboratories at UFZ Leipzig, where participants were able to view the procedues used for stable isotope analysis of environmental samples. The summer school was presented by researchers from the Helmholtz Centre for Environmental Research UFZ and University of Neuchatel.