The New Institutional Economics is sometimes referred to as “property rights” economics.  And yet the thin notion of property rights employed by economists bears at first glance little relation to the legal content of property.  This lecture will present an overview of the application of the New Institutional Economics to property and show how it can be extended to provide explanations of the structure of property law itself.  After considering some classic issues of directionality of causation and the evolution of property rights, the lecture will present recent applications of information cost economics to property and end with a case study of complex property rights in the open fields of medieval and early modern England.