This paper presents a new method for evaluating product designs at their early stage of development according to different criteria and a case-study-based project. The goal is to select among imprecisely defined design alternatives in a multicriteria context, as is required for taking into account sustainability considerations. Imprecision-the most dominant type of uncertainty during the early stages of design-is defined as designer's preferences for a range of values in the design variables; it can be modelled by fuzzy numbers. The project involves the analysis of three design concepts of a vacuum cleaner (paper bag, plastic bin with filters and plastic bin with cyclone). Using the proposed multicriteria decision method different End-of-Life (EOL) strategies for the three concepts are investigated from the viewpoint of four criteria (one economic and three environmental). Sensitivity analyses are performed to identify the parameters influencing the robustness of the decisions. The case study will show that the 'right' decision (i.e. the selection off between criteria performances.