We carried out complete active space multiconfiguration self-consistent-field calculations followed by multireference singles+doubles configuration interaction with the Davidson correction which included up to 3.55 million configurations employing relativistic effective core potentials on Pt-3+Au and PtAu clusters. Four low-lying electronic states were identified for Pt-3+Au. The (2)A(2) electronic state (C-3u) was found to be the ground state of Pt,Au. Spin-orbit effects were found to be significant. We also computed six low-lying electronic states of PtAu and four low-lying electronic states of PtAu+. The 5/2 ((2) Delta) and 0(+)((1) Sigma(+)) states were found to be the ground states of PtAu and PtAu+, respectively.