Given the economic downturn, various studies have indicated that complex, long-term relational contracts are commonly being renegotiated and varied in order to obtain cost reductions or to meet other strategic and tactical business needs. This chapter will seek to critically examine the doctrine of good faith in the variation of such contracts. It will use the relational contract paradigm to analyse how (if at all) the doctrine applies under English common law to the variation process. Using recent decisions it will consider how the doctrine of good faith seeks to regulate variation; how it understands and comprehends this area; what legal rules it applies and what assumptions it makes about the way parties should/might behave in such circumstances. In doing so this chapter will conclude that the current view of good faith under English common law does not meet the relational needs of such contracts upon their variation and will suggest that if the law is to meet the commercial needs of parties to relational contracts, it will have to reconsider the extent of any obligation to renegotiate in good faith.