The second ADVOCATE network summer school on the theme of Principles and application of flow and transport modelling in the subsurface, was hosted at the University of Liège, Belgium, on 27-30 August 2013. This event was attended by 21 fellows and external participants, who included researchers and professional environmental engineers from Europe. Over the four days the participants were introduced to the principles and limitations of subsurface flow and transport modelling, developing conceptual site models from soil and groundwater contamination scenarios for numerical modelling analysis, use of interpretation tools, such as inverse modelling and automatic calibration and model sensitivity analysis, and example applications for different problems. The participants had the choice of learning on one of three commonly-used modelling platforms, which covered 1-D, 2-D and regional (groundwater body-scale) applications, and a choice of typical groundwater contamination cases. They also had the opportunity to present their own case studies in overview for group discussion with the instructors. The summer school was presented by researchers from the University of Liège and VITO, with guest speakers from SCK CEN Mol (Belgium), University of Mons (Belgium) and Université Laval in Québec (Canada). And, on a lighter note, everyone got to join in the summer school BBQ !