As part of the MITHRAS program, the Chatanika and Millstone Hill incoherent scatter radars made coordinated observations of the polar ionosphere on June 27 and 28, 1981. The temperature data obtained during these days were compared with predictions made by a high-latitude ionospheric model. The comparison of the temperature measurements and the results of the ionospheric model depend on the assumptions made both in reducing the data and on the inputs that are needed by the model. The deduction of electron temperature from radar measurements depends upon a knowledge of the mean ion mass as a function of altitude. The model requires a knowledge of the heat flux at the upper boundary and the volume heating rate. The results of the model were compared with measurements for a variety of combinations of the required inputs. It was found that the best fits resulted with a heat flux of from 0 to −0.7 × 1010 eV cm-2s-1 at the upper boundary and a relatively high volume heating rate. These results also required that the model predictions for the average ion mass be used in the reduction of the radar data. However, other combinations of assumptions also produced good fits. A systematic temperature difference of between 200 and 300 K was found between the Chatanika and Millstone Hill measurements of electron temperature at high altitudes.