Ion composition at mesospheric altitudes has been measured at and compared between high- and mid-latitude sites under summer daytime conditions. Both rocket-borne measurements were made with pumped quadrupole ion mass spectrometers (mass range 15--145 amu). Apogee occurred below 90 km on each flight, subsonic sampling near the mesopause thus being possible. Water cluster dissociation was further minimized by using low attractive bias potentials of -5 V for each instrument. The mid-latitude data were obtained at Wallops Island, Virgina (latitude, 37.8¿N; longitude 75.5¿W), on June 30, 1973, at 1510 LMT (x=43¿). Large quantities of hydromium cluster ions were observed through 109+, with maximum concentrations at 55+ and 73+. Also cluster ions of nitric oxide were observed through 84+. The high-latitude launch occurred at Kirma. Sweden (latitude, 67.9¿N longitude, 21.1¿E), on August 2, 1973, at 0700 LMT (x=68.5¿), following visual sighting of a noctilucent cloud on the prior evening. The data near the mesopause show the typical cluster ions mentioned above but also a preponderance of heavy ions between 90 and 145 amu, with groupings 18 amu apart but unrelated to the more typical cluster ions. One possible set of consistent identifications leads to iron and iron oxide hydrates. These results may suggest the presence of metallic particulates and ions which form hydrated cluster ions within the cloud region.