In this report, FOI research on C3I during 2004 is summarized. The extent and the aim of the research area is shortly described. Also the national and the international evolution of the area is stated. The research activities, which have been performed by projects, are described to contents and results. The research area is divided into four main groups, Decision Support, IT Securty, Cammand & Control Concepts incl Methodology and Teckniques and Wireless Communications. The research has, in the period, been focused on the special problems, that are liable to the SwAF transformation into a Network Based Defence. Issues, which concern international interoperability and operations in an urban environment, have been paid attention to.