Cellular signalling processes are governed by a delicate balance of phosphatase and kinase activity. Over the past few years there has been considerable effort directed toward the development of kinase based therapeutic agents, whilst phosphatase based therapeutics have lagged. Herein we address key issues relating to selected therapeutic targets: malignancy, diabetes, immunosuppression, cystic fibrosis, asthma and cardiovascular disease. As part of ongoing studies we examine the recent developments in understanding the key interactions between the okadaic acid class of compounds and the serine/threonine protein phosphatases 1, 2A and 2B. Crystal structure and molecular modelling guided inhibitor development is also a key focus of this article.