Organic farming is widely perceived as being more environmentally friendly than conventional farming. As a form of sustainable agriculture, it receives substantial support from policy for its contribution to environmental protection as well as the provision of amenities such as biodiversity and cultural landscapes. Consumers are attracted to organic foods as they are produced without synthetic chemicals and comply with higher animal welfare standards. Although organic farming certainly has the potential to fulfil these expectations, studies have shown that some certified organic farms do not. Their practices comply with the regulations, but not with the principles of organic farming. This trend has been called 'conventionalisation' of organic farming. In this paper we review the studies that discuss the conventionalisation of organic farming, focusing on the farm level and on evidence from Europe. We argue that to strengthen organic farming's transformative potential, the debate must move beyond its focus on the bifurcation between artisanal and conventionalised organic farms, so as to capture the full range of empirical heterogeneity. Our core argument is that to adequately understand the dynamics within organic farming and their potential impact on the ability of organic farming to fulfil the expectations of consumers and policy-makers, it is not sufficient to focus on structural changes. Instead, we need to assess whether or not the observed changes comply with the principles and values that are the fundament of organic farming. [ABSTRACT FROM AUTHOR]