The implementation and certification of ISO 9000 quality assurance systems in Spanish agribusiness companies is a recent although rapidly growing phenomenon. In spite of the extensive biography available on ISO standards few works have been published on the experience from the companies' point of view. This article carries out an empirical analysis of the main motivations that encourage companies to set up an ISO 9000 quality assurance system and also the reasons that discourage them from doing so. The analysis of this latter aspect, using multivariate methodology, allows an in-depth examination of the series of problems that agribusinesses face.