Dedicated to Prof. Dr. Eckard Krtzig on the occasion of his 60th birthday.Five annealed BaTiO3:Rh crystals, including as-grown and those reduced at 10-5atm, 10-10atm, 10-12atm, and 10-14atm oxygen partial pressures, were produced and investigated by two-beam coupling at wavelengths of 514nm and 633nm. The carrier type is a function of reduction degree and incident wavelength. The compensation points are around 10-3atm and 10-11atm oxygen partial pressures for 514nm and 633nm, respectively. The electrooptic gain is controlled by the photoconductivitydark conductivity ratio, effects from the deep and shallow traps, and holeelectron competition, which are dependent on the reduction degree and incident wavelength.