Gray marketing, a term used in marketing ethics, refers to the ethically and legally questionable practices within marketing activities. It is difficult, even by applying laws, to take sanctions against some activities such as parallel importation, providing meals, giving gifts, offering kickbacks among others. Both purchasing and sales personnel may also be involved in gray marketing, oftentimes to benefit themselves at the expense of others. In gray marketing, purchasing and sales personnel turn into “the community of interests”, and for that reason they would never whistle blow on each other for the questionable or “gray” marketing behaviour. Because this attitude and practice is so deeply imbedded in many organizations, some gray marketing practices simply cannot be effectively stopped or controlled. To a large degree in many cases, gray marketing practices have evolved into a “hidden rule” in a given organization. As an unfair competitive method, gray marketing undermines the normal order of the market, and leads to unreasonable allocation of social resources. Gray marketing is a key contributing factor to business corruption, it effects and raises the market price, it oftentimes reduces consumption, and it may even poison the social climate and damage the interests of the enterprise and society as a whole. Gray marketing has already been brought forward, to both business and society, as an important ethical issue to be confronted. This research reviews the gray marketing theory by looking at moral philosophical theories, classic ethical decision-making models, and factors affecting ethical decision-making. This study proposes a conceptual model and ii seven hypotheses, which configure how the ethical policies influence personnel in purchasing and sales. The study will also provide an ethical evaluation pertaining to the relationship between ethical purchasing policy, purchasing personnel’s ethical evaluation of gray marketing, and purchasing personnel’s gray behavior tendency. Finally, this research tests the hypotheses with data collected using both factor analysis and multiple regression analysis.