The two volume set LNCS 5726 and LNCS 5727 constitutes the refereed proceedings of the 12th IFIP TC13 International Conference on Human-Computer Interaction, INTERACT 2009, held in Uppsala, Sweden, in August 2009.

The 183 revised papers presented together with 7 interactive poster papers, 16 workshops, 11 tutorials, 2 special interest group papers, 6 demonstrations, 3 panels and 12 doctoral consortium papers were carefully reviewed and selected from 723 submissions. The 91 papers included in the second volume are organized in topical sections on multimodal interfaces; multi-user interaction and cooperation; novel user interfaces and interaction techniques; social media/social networks; tangible user interfaces and robotics; tools for design, modelling and evaluation; usability evaluation methods; user experience; user interfaces for safety critical systems and health care; user interfaces for Web applications and e-commerce; and visualization techniques.