The inaccuracy and the uncertainty of complex systems can be represented in many cases by interval models.One of our lines of research is to develop methods and interval-analysis-based tools for the purposes of being able to work with these systems.The following tools have been developed by the research groups based on interval analysis - IvalDv: modal interval arithmetic - FSTAR: Internal and external approximation of the *- semantic extension of a continuous function.- QSI: Quantified Set Inversion - MINIMAX: limited optimisation - SQUALTRACK: detecting dynamic-system failures The interval analysis we have applied in several fields such as error modelling, simulation and detection, set inversion, optimisation problems, robust control analysis and design, computer graphics.