In the session ” Tumour: stroma interactions” presented at the 2015 National Cancer Research Institute (NCRI) Cancer Conference, the importance of stromal interaction in the tumour environment is discussed by Kairbaan Hodivala-Dilke, Ilirjana Bajrami, Helmut G. Augustin, Jason Fleming and host Erik Sahai. Whilst it has been realised for many years that cancer is a process driven by mutations within the cells, it is also clear now that those cells also have complicated interactions with neighbouring cells and the local environment. The focus of this session was to try to understand how the complex interactions between tumour cells and stroma affect the behaviour of cancer cells, both in their ability to metastasise and how they respond to therapeutic interventions.