Systems of Systems (SoS) can be described as a class of complex systems whose constituents are, themselves, complex (Jamshidi, 2009). They are characterised (Maier, 1998) as being composed of many heterogeneous systems that are geographically distributed, and independently managed and/or operated; SoS evolve over time (i.e. they are not designed at the outset, but are composed of interoperable systems that were not necessarily designed to work together when conceived). Most importantly, they exhibit emergent behaviour; i.e. behaviours that cannot be achieved by any of the systems independently, but which arise from the interactions of the component systems. SoS are recognised as a significant 21st century challenge affecting many highly networked domains, such as defence, transport, healthcare, service provision, and environmental sustainability. In all cases there is a need to better understand the enterprise nature of the domains and to enable human participants in such systems to cope more effectively with the increase in complexity that SoS imply. Current methods and approaches in ergonomics have generally been designed from a single systems perspective and may be inadequate in addressing SoS aspects associated with technical and organisational complexity, such as situation awareness, work load, roles and responsibilities, trust, knowledge management, organisational learning and competencies. This debate will consider the role of the ergonomics discipline in meeting the challenges of systems of systems, and seek to identify a research agenda that will generate new research techniques, ergonomics models, and practitioner tools that are adequate for the complex socio-technical environment of the 21st Century. The experiences of participants in the debate will be crucial to the generation of challenges and ideas to meet them in the context of systems of systems. It is anticipated that the conclusions of this debate will form the basis for new research agenda in applied ergonomics.