The study focuses on organized activities within communities experiencing disaster. It is initiated by a description of the nature of disaster involvement on the part of various community organizations. A discussion follows of the different meanings of the term 'disaster' and of the social implications created by differential characteristics of disaster agents. It is suggested that the primary disruption of the social structure is revealed in unplanned changes in interorganizational relationships. Four types of organized behavior are isolated, derived from a cross-classification of the nature of the disaster tasks and the post-impact structure. Using these four types, problems of mobilization and recruitment are discussed as well as the specific operational problems these groups experience functioning under disaster conditions. A final chapter deals with the implications of disaster research in dealing with the organizational consequences of a nuclear catastrophe.