The present thematic volume of the Alma Mater Series contains the delivered papers of the 1st International Conference on the Theory of Information Retrieval.It is commonly agreed that the term 'information retrieval' (IR) refers to fetching information, relevant to users' information needs. It uses recorded information from primarily, although not exclusively, (generally networked) computer systems. As such, IR -- building firmly on its library science roots -- has by now proved to stretch beyond information and computer sciences, reaching mathematics and linguistics, tackling and challenging new areas like physics, philosophy, sociology or biology.It was the broad goal of the ICTIR’07 to be the forum that reflects just this new, multi-valued meaning of IR in terms of new and original results. It was a great opportunity for presenting, discussing, analyzing and integrating new theoretical results in IR, including the traditional and already well-established fields and approaches in this subject, as well as to welcome new approaches coming from other scientific areas.