Multi-organizational ad hoc knowledge networks have the potential to improve the effectiveness of disaster response and recovery by helping organizations share information, coordinate their activities and leverage participants' expertise. This paper reports an exploratory study to identify the major barriers to effectiveness in ad hoc knowledge networks in disaster response. The research methodology is a multi-panel Delphi survey, with each panel comprised of experienced emergency response professionals from different types of response organizations (e.g., fire fighters, EOC (emergency operations center) directors, law enforcement professionals). The study is currently in progress, and results from the first two panels are reported.