High-latitude upper mesospheric neutral winds are investigated for evidence of a response to changes in the level of geomagnetic activity through a cross-correlation analysis using AE and Kp. A consistent and significant causal response within several days of intervals of increased activity is not evident in the neutral wind data from 80 to 90 km altitude. Instead, through cross correlation with the neutral wind data set, the low-frequency components of the AE and Kp data sets have been identified. These results, in conjunction with other recent studies, indicate that it is above 90 km, in the lower thermosphere, that magnetospheric forcing first becomes significant for affecting neutral dynamics at high latitudes. ¿ American Geophysical Union 1988