An experimental and analytical program has been performed to study the temperature distri bution, as a function of reactor power, in the TRIGA reactor at The Pennsylvania State Uni versity. A two-dimensional digital computer pro gram written in FORTRAN language numerically solves Poisson’s heat equation using finite dif ference techniques. Experimental measurements of the fuel tem perature in the core midplane and in the water over a large portion of the core are incorporated into the computer code, which permits determin ing the temperature distribution through the core as a function of power. Several interesting re sults were obtained, one of which showed that sub cooled boiling commences in the core between 150 and 200 kW.