We report absolute differential cross sections for charge transfer scattering of 0.5--5 keV O+(4S) ground state and O+(2D, 2P) metastable ions by atomic oxygen at angles between 0.04¿ and 3¿ in the laboratory frame. Absolute total charge transfer cross sections, derived from these measurements, are compared with previously published data. The measurements were made using a flowing gas target, which consisted of a mixture of atomic and molecular oxygen produced by passing O2 through a microwave discharge. The atomic oxygen cross sections were obtained by appropriate subtraction of the signal due to molecular oxygen from that due to the mixture of O and O2. These data are relevant to model calculations of energetic O+ precipitation into the upper atmosphere and to the diffusion of low-energy O+ ions in the ionosphere. ¿ 2001 American Geophysical Union