Designing more sustainable processes is one of the key challenges for sustainable development of the chemical industry. This is by no means a trivial task as it requires translating the theoretical principles of sustainable development into design practice. At present, there is no general methodology to guide sustainable process design and almost no practical experience. In an attempt to contribute to this emerging area, this paper proposes a new methodology for integrating sustainability considerations into process design. Underpinned by life cycle thinking, the methodology guides the process designer through different design stages to enable integration of technical, economic, environmental and social criteria. The approach is illustrated on a design case study of the vinyl chloride monomer process. The case study shows how to identify relevant sustainability criteria, how to assess the level of sustainability and how to use the obtained information to make the design more sustainable.