Energetic neutral atom (ENA) detectors have been successfully flown on missions such as the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) and are now an important tool for probing the geospace environment. Interpretation of ENA data, however, requires knowledge of a number of key charge transfer cross sections. Here we present a critical review of the published experimental measurements and recommend a set of parameterized cross sections. The processes considered are charge transfer of H+ and O+ with H, O, N2, and O2 for collision energies from 10 eV to 100 keV. The limitations of the measurement techniques and the probable reliability of the recommended cross sections are addressed.