The spectroscopic properties of the trans isomer of four 4-R-4'-nitrostilbenes (I-R, R: H, OMe, NH2, NMe2) in solution at 25 degrees C were studied by time-resolved absorption techniques. An absorption increase within 10 ps and the subsequent decay in the visible range are attributed to the excited singlet state (S-1 --> S-n transition). The lifetime for this decay (tau(S)) varies for trans-I-NMe2 from 1-3 ns in solvents of low polarity to congruent to 10 ps in acetonitrile. Also for trans-I-NH2 and trans-I-OMe, tau(S) is sensitive to the solvent polarity. In those cases where the quantum yield of intersystem crossing is substantial, the transient absorption due to the T-1 --> T-n transition at an appropriate wavelength, increases with almost the same lifetime and then remains constant.