PVC (polyvinyl chloride) is currently one of the most produced and used plastic materials, although its' development has been far from straightforward. This paper describes how this material, from its early commercial production on until recently, has been subject to various criticisms concerning health and environmental hazards, but despite and thanks to these criticisms became deeply entrenched in society. Hughes' systems approach proves useful to understand this history; various ways of how the PVC industry has been dealing with reverse salients are revealed. However, to understand these processes, the systems approach has to be broadened with a network-oriented perspective. Outside influences on the system have to be accounted for, as well as negotiation processes between different (sub) systems. Finally, the PVC history suggests that the dynamics of the inter-system relations might be used for de-entrenchment strategies, by addressing higher system levels or overlapping systems, or by stimulating the entrenchment of alternative (sub) systems.