Need is a major concern when designing a new product and, consequently, need analysis is a key task during the front end of innovative projects. However, need remains a paradoxical concept, something that everyone feels, accepts and understands, but is difficult to model. This research contributes to the theoretical and methodological aspect of need. To elaborate a need analysis methodology adapted to the first steps of innovative projects, a literature review highlights the main characteristics of this concept and collects definitions within a large scope of disciplines. Based on these theoretical elements and on a systemic approach, a model is suggested to describe the needs of targeted stakeholders. This model aims at the treatment of descriptive data concerning the functioning modes of customers and other involved stakeholders in order to define individual needs. An example of application of the method is detailed among a large panel of experimental innovative projects.