This volume contains the proceedings of the Fourth International Conference on Mathematical Knowledge Management MKM 2005 held July 15–17, 2005 at - ternational University Bremen, Germany. Previous conferences have been at the Research Institute for Symbolic Computation (RISC) Linz, Austria (September 2001), at Bertinoro, Italy (March 2003), and Bialowiecze, Poland (September 2004). Mathematical knowledge management (MKM) is a field in the intersection of mathematics and computer science, providing new techniques for managing the enormous volume of mathematical knowledge available in current mathematical sources and making it available through the new developments in information technology. The annual MKM Conference brings together mathematicians, software - velopers, publishing companies, math organizations, math users, and educators to exchange their views and approaches, current activities and new initiatives. For the first time, MKM 2005 chose to have post-conference proceedings, as otherwise the submission deadline would have collided with other conferences and crimped time since MKM 2004 in September 2004. The decision also faci- tatedkeepingtheconferenceopentonewideasaswellaskeepingupthematurity of the papers necessary for inclusion into archival proceedings. With a May 15 deadline, MKM 2005 received 38 submissions. Each submission was reviewed by at least three programme committee members. The committee decided to - cept 27 papers for presentation at the conference. Out of these, 26 papers were accepted for publication in the conference proceedings after re-evaluation by the Programme Committee since they included significant improvements triggered by the referee reports and the discussions at the conference.