Optical absorption and related characteristics in undoped, semi‐insulating GaAs crystals have been investigated, especially at the bleaching and thermal recovery stages. It has been shown that a broad absorption band at a longer wavelength grows as bleaching proceeds, in a reciprocal relation with the near‐infrared absorption band. It has been found that the bleached near‐infrared absorption shows rather abrupt recovery at a temperature around 130 K and that the recovery profile, i.e., the temperature derivative of the recovering absorption, is dependent upon the crystal composition and thermal prehistory. Hence, the present method, recovery characteristics of the bleached absorption method, may have applicability for elucidating defect properties as well as crystal characterization. Simultaneous measurements of extrinsic photoconductivity combined with related experimental results have lead to a conclusion that the extrinsic photoconductivity in the enhanced state is related to the metastable state of the deep lying defects. These experimental results are discussed systematically on the basis of the defect transition to and recovery from the metastable state.