We report the first microwave detection of atmospheric NO, obtained through ground-based observations of 250.796 GHz (1.2 mm) line emission from lower thermospheric NO. The observations were conducted with the National Radio Astronomy Observatory (NRAO) millimeter telescope at Kitt Peak, Arizona (32 ¿N, 111 ¿W) on April 1--3, 1991. The thermal linewidth of the measured NO spectrum corresponds to an average atmospheric temperature of 300 K which, combined with the observed lack of pressure broadening, places the origin of the NO emission at altitudes of 100--120 km. The thermospheric column (altitude >70 km) density of NO inferred from the observed line emission is 5.0-1.0+1.5¿1014 cm-2, indicating extraordinarily high abundances of lower thermosphere NO for the current solar maximum period. During the three days of observations, the NO line emission did not exhibit diurnal or daily variations to within the 10--15% measurement uncertainties. ¿ American Geophysical Union 1992