In order to reduce time to market and to master the costs, the design process of industrial companies is more and more structured. It enables collaborative design for experts integration and for improving the decision-making process. Decision making under uncertainties remains an important issue, especially at the beginning of this design process. The product performances are a common reference in collaborative design, and their management involves interactive design. In this paper, a functional analysis under uncertainties approach is proposed, as a means to improve interactive design. It enables to manage the risk of not fulfilling the required performances throughout the design process. This methodology makes it easy to link the data usually handled in engineering design (especially the technical requirements) with those handled for risk assessment (especially failure analysis). Using logical trees, the product functions and the associated chosen technologies are analyzed in terms of risk, taking account of the uncertainties that lead to risk and the potential failure that can arise.