[en] The thermal-hydraulic analysis code ''TEMDIM'' is used for the calculation of the two dimensional temperature distribution, the coolant flow distribution in each flow channel, the thermal stress and the thermal deformation, and the estimation of hot spot temperature in the core of high temperature gas cooled reactors and other any type of nuclear reactors. The outline of the analysis flow chart, the characteristics of each calculating part, the basic equations, the calculating procedure of this code are explained. The analysis models consist of the channel temperature calculation model ''PLANDY'', the coolant flow calculation model ''SIZUKA'', the thermal stress and displacement calculation model ''DEFORM'', and the hot spot temperature calculation model ''HSPOT''. The analysis example using this code is shown for the core of a high temperature gas cooled reactor with four orifice regions and two types of fuel assemblies. Several technical problems to be improved in the future are pointed out for expanding the use of this code to the special field. (Nakai, Y.)