Chegyong Im. 2001. Person Constraint and Licensing of Expletive Constructions. Studies in Modern Grammar 25, 29-53. Some structures allow number agreement but not first/second person agreement. That would follow if the [person] feature of T reduces to [3 person] (the default choice). We will show, in this paper, the environment in which this phenomenon happens, suggesting a universal constraint for the locative inversion constructions and expletive constructions. The other major purpose of the paper is to illustrate the licensing of expletive constructions in the framework of Rizzi (1997) and Platzack (2000). We argue that the different syntactic behavior between there type expletives and it type expletives can be explained in terms of Multiple Interfaces. We will also try to show that the structure of TECs in Icelandic can be neatly identified in our proposal.