The practice of eco-design requires relating traditional design criteria to new environmental criteria. So far, few studies have investigated the nature and singularities of eco-design. This article provides some elements of response based upon the redesign of a consumer product (disposable razor). The study was conducted by three groups of experienced eco-designers using existing eco-design tools (SIMAPRO, ECOFAIRE, ECODESIGN PILOT). A protocol analysis with a three-level coding of transactions was carried out for this purpose. Two main findings are reported: (1) environmental assessment, solution finding and strategy definition are the activities which differentiate eco-design from design; (2) environmental initial assessment and strategy definition are more heavily influenced by eco-designers' expertise than support from tools