Whether a trade ban on a product imposed because of the fact that the process-and-production-method (PPM) of that product is harmful to the environment can be consistent with the WTO law? The purpose of this paper is to trace what the panels and the Appellate Body of the WTO have done in settlement of disputes concerning this problem and especially to think about a possible 'evolutionary' role the Appellate Body can play in resolution of 'trade and environment' disputes. This paper begins first to consider generally the essential characteristics of the problem of so called 'trade and environment' and then to identify a special problem which is raised by these characteristics in the context of the dispute settlement system of the WTO. Second, in a more substantial level, this paper will consider what a trade related environmental measure (TREM) based on a PPM is and then identify the issues of its possible inconsistency with the WTO law. Third, we will trace how the panels and the Appellate Body have disposed of these issues in practice and also make some analysis of a new approach adopted by the Appellate Body in interpreting the WTO law in recent two cases. In conclusion, this paper will affirmatively evaluate this new approach and remark that the Appellate Body does not need to 'live with a quiet but uneasy status quo' in the 'trade and environment' disputes.