A Fabry-Perot interferometer has been used to determine midlatitude thermospheric wind velocities and temperatures during the large geomagnetic storm of March 26, 1976. These quantities were determined from the Doppler shifts and broadening of the twilight and nightglow 630.0-nm emission line observed from the Laurel Ridge Airglow Observatory (40¿8' N, 79¿10' W). Following the onset of the storm at ~0300 hours UT, the wind vector increased from a twilight, quiet period value of ~100 m/s (eastward) to a maximum of ~600 m/s, directed generally southward. Large velocities (>200 m/s) persisted from ~0400 hours UT to the end of the observing period (~1100 hours UT) and were generally larger by a factor of ?2 to the north of the observatory than to the south. A temperature rise of ?500 K during the course of the storm was noted in all directions, with pronounced, relatively rapid fluctuations (of up to 600 K) to the north.