Résumé : This document reports on a work carried out in the areas of cognitive modelling and knowledge representation. Two specific and complementary issues are addressed. The first one is concerned with modelling reasoning strategies used by experts from different specialities in the domain of accidentology. This model ling task is grounded on our previous work carried out in medical problem solving. The second issue is centred on representing those reasoning strategies with the con ceptual graph formalism. The approach to build the typologies of concept types and relation types as well as the conceptual graphs in the domain of accidentology is experimental as we use a computer-based tool dedicated to conceptual graphs, deve loped in the ACACIA project.