Summary The term cognitive tool was coined for a means especially designed to improve human cognition. Examples of cognitive tools range from simple mind maps to computer-based assistence systems. Cognitive tools can play a key role in the knowledge management process. This paper describes specific requirements for cognitive tools in a medical context, and presents an implemented framework for enabling medical knowledge management by cognitive tools. The visualization of semantic networks and the users interaction with these graphical metaphors play an important role not only in the process of authoring or knowledge externalization, but in the computer-supported application and internalization of medical knowledge, as well. The paper addresses special methodological aspects, namely: 1) the seamless integration of formal knowledge representation and informal knowledge documentation, 2) the introduction of graphical means for interacting with the medical knowledge, and 3) the mutual support of eLearning and knowledge management. The framework is applied to complementary fields: 1) a learning system for differential diagnosis in paediatrics and 2) a tool, which empowers scientific literature retrieval by a graphical visualization of concept-nets based on the Medical Subject Headings (MeSH). As a result the case studies show that a generic framework, which supports the visualization of conceptual structures and allows an easy interaction with a medical knowledge repository can successfully support very different steps of medical knowledge work and clinical decision support.