Temperatures obtained from FORMOSAT-3 and COSMIC observations in the stratosphere are analysed for tidal variations. It is seen that non-migrating tides are not very significant in the high-latitude winter stratosphere. It is shown that the observed amplitudes of these tides in earlier studies are most probably a result of aliasing and are not geophysical in nature. Thus, the process of non-linear interactions through which it was believed that they are produced seems to be unimportant.