Considerable progress has been made recently in elucidating the importance of various solar tides in generating winds, electric currents, and polarization fields in the ionosphere. From incoherent scatter radar observations at Arecibo, St. Santin, and Millstone Hill it appears that high-order (2,4) and (2,5) semidiurnal tides dominate in the height interval 105--125 km and contribute significantly to the generation of the solar quiet (Sq) dynamo current. These tides are thought to be excited by energy coupled out of the fundamental (2,2) semidiurnal mode in the mesosphere through the presence of background winds. This paper suggests that by analogy with the behavior of the solar thermal tides the lunar gravitational (2,2) tide also may generate higher-order modes. In this event, lunar tidal influences on the ionosphere, which invariably have been attributed to the (2,2) mode, should be reexamined. It appears that phenomena such as the lunar height variations of the E layer might better be explained as arising from the lunar (2,4) rather than the fundamental (2,2) mode.