The degree of interaction between atmospheric gravity waves and tides is an issue which is of great importance in middle atmosphere studies. It is especially important with regard to tidal variability which is frequently observed in the mesosphere and lower thermosphere, but as yet has not been subject to adequate study. In this paper, we present some strong observational evidence of such interactions made with the UWO 2 MHz radar near London, Canada. Our observations show significant correlation between gravity waves and tides (diurnal) at certain times of the year, and the nature of the correlation is intermittent and varies with time of year. It is possible that differences between tidal amplitudes at sites with mesoscale separations may be explained in terms of such phenomena. We also propose a simple model which is found to be consistent with the major features of the observed data. ¿ American Geophysical Union 1995