Calculated energy levels of highly excited sodium atoms in an electric field are presented. The energy levels have been computed in the low ( to .4 V/cm) and intermediate (.2 to .4 V/cm) field regions for the 34^3/2,5/2 states, and in the high (up to 6 V/cm) field strength regions for the n = 15 states. At low field strength, all the 34^3/2,5/2 states are found to decrease in energy with increasing field strength. The method used to calculated the energy levels is outlined. The results are compared with second order perturbation theory and with experimental data obtained using the method of quantum beats to measure the energy difference between states.