Complete active space MCSCF (CASSCF) followed by first-order configuration interaction (FOCI) calculations are carried out on low-lying electronic states of GaAs and GaAs+. Among the 12 electronic states of GaAs considered here, six of them are bound and their spectroscopic properties are calculated. The ground state of GaAs is found to be 3∑− with a 3Π state only 1569 cm−1 above the 3∑− state. The ground state of GaAs+ is found to be 4∑− state. The vertical ionization potential of GaAs is calculated to be 5.91 eV. Our calculations predict the electronic spectra of GaAs and GaAs+ which are yet to be observed.