We present a methodology for developing multimedia information systems. These latter are considerably different from the traditional ones because they deal with very complex and heterogeneous data such as sound, still-image, text and video. The complexity of data is principally due to their dependency of time. During their presentation, multimedia data must be synchronized on both temporal and spatial scales. We define a conceptual object model and give an outline of a design methodology. The presented model is a combination of object oriented concepts and Allen’s relations. In order to make the designer task easier and to help him during the development of his model, we have based this latter on existing formalisms such as those offered by OMT. The defined method is based on the object specification, and a number of models that are designed during the development process according to the water-fall approach.