In order to make recommendations for improving interoperable communications systems, this report from the Public Safety Wireless Network (PSWN) Program assess lessons learned from the attack on the Pentagon on September 11, 2001. In order to determine the initial state of wireless communication at the Pentagon following the September 11th attack, the PSWN Program conducted 32 interviews with first responders, technical representatives, and public information officers from the public safety agencies that provided immediate emergency response. Inquiries concerning the effectiveness of the technical and operational solutions used at the Pentagon were analyzed assessing the responses of fire and police departments and Federal law enforcement and other agencies. After discussing the Arlington County 800 megahertz (MHz) radio system providing communications for a majority of the first responders, this report details both compatible 800 MHz systems and incompatible equipment that forced some law enforcement agencies to be reliant on other means of communication. Describing other technologies available to responders of the Pentagon attack and the effect these had on operations, this report presents findings regarding the interoperational communications at the site of the Pentagon attack. After arguing that well-organized regional responses and pre-incident training greatly reduced the confusion for responding agencies, this report notes that commercial service networks were not deigned to handle the immense volume of calls generated at the incident scene. Presenting a series of recommendations, this report argues for the proactive efforts of the Washington Metropolitan Council of Governments, for increased training and drills, for the use of the incident command system in response to crisis situations, for the development of a regional or statewide communications system, and for the adherence to common technology standards in regard to implementing future public safety communications systems. A series of appendices providing data collection materials, mutual aid agreements, and a list of acronyms compete this report.