This book constitutes the refereed proceedings of the 6th International Conference on Ubiquitous Computing and Ambient Intelligence, UCAmI 2012, held in Vitoria-Gasteiz, Spain, in December 2012. The 70 research papers were carefully reviewed and selected from various submissions. The main focus of this book has been to explore how Ambient Intelligence can contribute towards smarter but still more sustainable environments. Beyond sustainable computing the proceedings also include research work describing progress on other key research topics for AmI such as human environment mobile-mediated (through NFC or AR) interaction, artificial intelligence techniques to foster user- and context-aware environment adaptation, future internet trends such as social networks analysis, linked data or crowd-sourcing applied to AmI, internet-connected object ecosystems collaborating to give place to smarter environments.