Through comparative sociological analysis, this paper discusses the patron-client relation in urban locality groups. The civil defense groups as urban locality groups which emerged during the chaotic situation after the Kanto earthquake in September 1923, and during Jakarta riots in May 1998, are the subjects of comparison. Even though the social background and historical context of the societies in question are different, both incidents share some similarities, in the rumors which accelerated the formation of civil defense group in almost every neighborhood. Further analysis on the formation, membership, and activities of the group reveals that the patron-client relation is not a mere power (vertical) relation, but also a life-cooperation relation. © 1999 The Japan Sociological Society.