Potential energy curves and spectroscopic parameters of several electronic states of the KO molecule have been calculated using multi-configurational methods. The KO B 2(Pi) state, first time theoretically described, presents a strong avoided crossing with the A 2(Pi) state, and allows for the explanation of the observed fluorescence of the KO molecule. Eleven electronic states have been studied at all the internuclear distances. Effects of complete active space and basis set selections on the results are also analyzed.