The SPS Agreement is one of the most innovative and controversial aspects of the World Trade Organization (WTO). This agreement uses science as a benchmark for assessing the legality of Member State regulation and has, in high profile cases such as EC Hormones and EC Biotech, been used to condemn regulatory measures as unlawful. The agreement, and the institutions which develop and apply it, walk a precarious middle line between trade and public health/environmental protection. This lecture will examine and evaluate the operation of this agreement, both before the WTO ‘courts’ and in the more co-operative setting of the SPS Committee.