this book constitutes the refereed proceedings of the 12th international workshop on groupware, criwg 2006, held in medina del campo, spain, in september 2006. the 21 revised full papers and 13 revised short papers presented were carefully reviewed and selected from 99 submissions. the papers are organized in topical sections on collaborative applications and group interaction, group awareness, computer supported collaborative learning, languages and tools supporting collaboration, groupware development frameworks and toolkits, collaborative workspaces, web-based cooperative environments, mobile collaborative work, and collaborative design.