The O II (2P-2D) transition at 7319 and 7330 ¿ has been examined in the dayglow for several orbits by using the complement of instruments on the Atmosphere Explorer C and D satellites. Production of O (2P) ions in the daytime is primarily due to photo-ionization excitation of neutral atomic oxygen. The ionization frequency at zero optical depth for production of O+(2P) ions is found to be 4.5¿108 s-1. The O+(2P) ions are lost by radiation and are quenched by O, N2, and electrons. The derived quenching rate for O is 5.2¿1011 cm3 s1, and the quenching rate for N2 is found to be 4.8¿1010 cm3 s1. The theoretically determined electron quenching rate is compatible with the data.