A rocket measurement of thermospheric nitric oxide (NO) is used to evaluate the production of odd nitrogen by solar soft X rays (18--50 ¿). The rocket observation was performed over White Sands Missile Range on November 9, 1981, at 1500 LT for solar maximum conditions (F10.7=233). The peak observed NO density was 6.3¿107 cm-3 at 102 km. A photochemical model which included soft X rays was used for comparison with the data. The soft X rays create photoelectrons which lead to enhanced ionization of N2 and thus increased odd nitrogen production. A good fit to the data was achieved using a soft X ray flux of 0.75 erg cm-2 s-1. ¿ American Geophysical Union 1990