This paper is an attempt to discuss the concept of validation when applied to marketing models. It is suggested that "validity" is a highly complex notion that the marketing scientists inherited from various other disciplines. Unfortunately, pre-existing conceptions about validity bear little relevance to the specificity of the marketing context, hence a new framework is proposed in order to take into account the requirements of this context when validating a marketing model. Various aspects of marketing models verification are reviewed and a taxonomy of approaches to validation operations is put forward. The second half of the paper is devoted to a practical example of a validation exercise dealing with a micro-model of the new product adoption process; special emphasis is given to the role of management in specifying and carrying out the validation task.