Direct access to the triplet emitting state from the ground state is observed for Pt(II) complexes containing heterocyclic (C boolean AND C', C boolean AND N, N boolean AND N') and bis(diphenylphosphino)alkane (P boolean AND P') ligands. Extinction coefficients for such transitions are in the range 4-25 M-1 cm(-1). Emission quantum yields resulting from singlet-to-triplet excitation are as high as 61-77 times the emission quantum yields resulting from singlet-to-singlet excitation at 296 K. The intersystem crossing quantum yield from the singlet excited state to triplet emitting state is lower than 2% at 296 K but is greatly enhanced at 77 K. The forbidden electronic transition observed for Pt(II) complexes is attributed to result from spin-orbit coupling due to the presence of Pt(II) in the skeleton structure. The importance of excitation spectra on the computation of emission quantum yields is discussed.