This paper describes the use of mobile agent technologies in building a framework for the mobile information retrieval systems. A Mobile Agent Carrier Environment-MACE is first introduced. It is designed in allusion to a new computation notion called the service-on-demand. A specially designed protocol, the Service Protocol, provides an easy and flexible way of building service based applications. Based on the MACE, a framework is then established for mobile information systems. The framework supports remote information retrievals for mobile platforms, such as laptop computers or PDAs. It uses both fixed and mobile agents for carrying out information access in a variety of ways. Specific service stations are also included in the framework to cope with the difficulties arose from the unique characteristics of wireless networks.