Paul Lewis Joskow has long been recognised as one of MIT’s foremost applied economists of industrial organisation. I discuss Paul’s research under three main headings: regulatory economics, applied contract theory, and energy and environmental economics. What is impressive about Paul’s work is the range from theory through to empirical work and his attention to institutional detail. A recurring motif is that he challenges lazy calls for deregulation by carefully pointing out the conditions under which deregulation can work and where the need for continuing regulation lies. All of this he does in the context of listening carefully to what regulators and industry players say about the issues they face, the decisions they need to make and how their industries actually function.