This constraint, which is extremely robust cross‐linguistically, is known as the
person case constraint
(PCC), comes in several versions (Strong, Weak, Ultrastrong, and Me‐First), and has been related to a number of other phenomena showing restrictions on person agreement. This survey concentrates on different syntactic approaches to the PCC, as these have been developed in the past 15 years or so, focusing on the question of the scope of the constraint and its relation to comparable agreement restrictions in other domains. After presenting the different versions of the PCC and summarizing its main properties, I discuss some representative approaches to the Strong PCC based on Agree and relate Strong PCC effects to comparable restrictions. I then focus on the Weak PCC and the proposals that have been put forth to derive the various versions of the PCC on the basis of parameterizations of properties of Agree. I finally critically discuss (i) a proposal that has treated the PCC in terms of cartography and (ii) a functional, frequency‐based approach.