In this book, which is a revision and expansion of Naert and Leeflang' s Building Implementable Marketing Models (1978), the authors discuss in detail the model-building process. They distinguish four parts in t his process: specification, estimation, validation and use of models. Throughout the book, the authors provide examples and illustrations. T his book will be of interest to researchers, analysts, managers and st udents who want to understand, develop or use models of marketing phen omena.