Efforts to realize Web service technology for dynamic integration of distributed components have been started. There is also a proposal for a language that describes the integration flow in a platform‐independent form. It is expected that Web service integration will be applied not only to the Internet, but also to various environments such as pervasive networks composed of mobile devices with wireless connections. In the latter case, it is necessary to deal with resource saving problems such as those that arise in a relatively low speed and unstable wireless channel. This study applies the mobile agent technique to the above problem and proposes a mobile agent system for Web service integration. In the proposed system, the physical actions of the mobile agents, that is, migration and cloning, are separated from the integration logic, and are represented as rules to be added to the integration flow description. By this separation, the physical behavior can be added or modified according to environmental conditions without modifying the integration flow. © 2005 Wiley Periodicals, Inc. Syst Comp Jpn, 36(11): 34–48, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.20334