There is increasing evidence that the immune system regulates tumour progression and perhaps even tumour initiation. Hence, the debate has shifted from whether or not tumours are visible to the immune system, to how tumours are detected, to the complexion of the ensuing functional response (host-protective versus immunosuppressive), and to how that response may evolve over time. Clearly, an improved understanding of these points could influence clinical approaches to monitoring tumour progression and to therapy. To gain such an improved understanding and to apply it requires diverse experimental approaches that will collectively be represented at this session. Thus, there will be consideration of how the initial responses of inflammatory cells to cell transformation can be imaged in vivo by use of zebra fish. These results provide important information about the context in which immune surveillance may be initiated. Such innate surveillance may, in vertebrates, preface adaptive responses to tumour cell antigens whose identities and key features are subject to intense investigations. The session will consider how such ‘antigen optimisation' is now moving into a clinical immunotherapy context. Most likely, antigen-specific immunotherapeutic responses will only sustain if their natural evolution toward a suppressed state is opposed. A candidate route to achieving this would be to block molecules that naturally inhibit T cells in the late stages of immune responses. As the session will consider, multiple applications of this approach are showing encouraging safety and efficacy data when employed against major solid tumour targets. In sum, the session will provide evidence of substantive progress in immunotherapy and the existence of solid research programmes for the future optimisation of promising clinical strategies.