The optical spectrum of the PtN radical has been observed directly for the first time. The strongest band system [(0,0) bandhead at 18591 cm(-1)] displays an unusual "perpendicular Delta Omega 0" perturbation which gives rise to strong intensity cancellation effects. Although a (4) Sigma(-) ground state was expected for PtN, we have assigned the ground state as (II)-I-2,; a (4) Sigma(-) assignment is not consistent with our observations. We have used arguments based on both molecular orbital theory and atomic-ion-in-molecule theory to explain the observed ground state symmetry in light of the observed hyperfine structure. Four electronic bands involving a total of six Hund’s case (c)[v,Omega] substrates have been rotationally analyzed, and many more bands have been observed at lower resolution. The ground state was found to have Omega=0.5 and its principal constants are B-e=0.455708(5) cm(-1), alpha(e)=0.003448 1(1) cm(-)1, spin-rotation constant gamma(0)=0.06126(7) cm(-1) w(e) =947.0(5) cm(-1), and w(e)x(e)=5.0(5) cm(-1). Two other Omega states were observed at low energies-an Omega=1.5 state at T-e=2985.665(2) cm(-1), with B-0=0.445233(8) cm(-1), q=1.522(5)x10(-6) cm(-1) , w(e)=901(1) cm(-1), and w(e)x(e)=8(1) cm(-1), and another Omega=0.5 state with T-e undetermined and other constants remarkably similar to those of the ground state (B-0=0.45307(6) cm(-1), gamma(0)=0.06202(4) cm(-1), w(e)=947(1) cm(-1), and w(e)x(e)=5(1) cm(-1)).