This paper discusses issues related to the design of software tools that support learners in their participation in network-based learning activities. To guide the development and use of a new class of educationally-oriented network tools, this paper proposes a cognitively-based, distributed network learning framework (DNLF). This framework has three main aspects: (1) network mediators and the flow of information and knowledge; (2) networks and cognitive theories of learning; and (3) the human-network interface. As an example of an application of the DNLF, an ongoing research and development project is described that involves an electronic mail program called The Message Assistant is described. The Message Assistant is designed to promote higher order learning goals as a part of instructional activities conducted over distributed educational networks. In addition to the standard electronic mail features such as creating, sending, receiving, and reading messages, this program includes a user-defined incremental expert system and hypertextual linking functions to assist network users in their evaluation, organization, and distribution of network information and knowledge. Research using the DNLF can provide insights into important aspects of electronic educational networks and help guide the design of tools to better support learning in these rapidly evolving network environments. Six figures illustrate The Message Assistant screen displays. (Contains 14 references.) (Author/ALF)