This thesis explores the conditions to improve collaborative behaviour between organizations in crisis response management. It takes an explorative approach and begins by identifying several challenges to interorganizational collaboration. A systematic review of the international scientific literature in conjuction with semi-structured interviews with crisis management professionals in civil-military collaboration context identified several challenges and their underlying reasons.Indications on ways to minimize such challenges are also explored. Based on these indications, two factors are chosen that are tested with the help of experiments involving 111 crisis management professionals from the Swedish police force, fire and rescue services, defense forces and the Civil Contingencies Agency (MSB). The experiments were performed to test whether changing the degree of these factors can potentially influence collaborative behaviour. Findings of the study indicate that by changing familiarity and expectation of future cooperation the extent of utilizing resources and the extent ofcontributing resources can be influenced. With greater degree of familiarity and long term commitment between organizations, greater knowledge on capabilities and equipment of other actors in crisis response, there is a higher extent of utilization of resources from other organizations in a joint task. Similarly higher degree of familiarity and long term commitment also make organizations to be more willing to contribute in terms of resources, equipment, knowledge and capabilities in a joint task. This means by fostering higher degree of familiarity and long term commitment, organizations areexpected to share, allocate and mobilze resources between them more effectively. Since this most likely will contribute to improve overall collaborative efforts in crisis response management, steps to increase familiarity and long term commitment between organizations seem to be a promising strategy to improve interorganizational collaboration. The thesis also discusseshow increased familiarity and long term commitments may also help organizations to adapt to changed conditions that arise during crises. The thesis has implications for crisis planning, preparedness and overall improvements of collaborative efforts in crisis response management.