A weekly programme of water quality monitoring has been undertaken by the FSC’s Field Centre at Slapton Ley since 1970. Samples have been collected from the main streams draining into the Ley and from the Ley itself. The main purpose of this paper is to make available an online archive but in so doing the opportunity has been taken to update previous publications. Not surprisingly, given the ongoing eutrophic status of the Ley, most attention has been paid to the nutrients nitrate and phosphate; this review broadens the scope to include other water quality records. In relation to eutrophication, there are clear signs of improvement in the influent streams, but concerns remain about water quality in the Ley itself.