Ultrafast relaxation dynamics of the S-2 and S-1 states of 4,4'- bis(N, N- dimethylamino) thiobenzophenone (Michler's thione, MT) have been investigated in different kinds of solvents, using steady- state absorption and emission as well as femtosecond transient absorption and fluorescence up- conversion spectroscopic techniques. Steady- state fluorescence measurements, following photoexcitation to the S-2 state of MT, reveal weak fluorescence from the S-2 state (phi(F) similar to 10(-3) in nonpolar and 10(-4) in polar solvents) but much weaker fluorescence from the S1 state. Yield of fluorescence from the S-2 state is reduced in polar solvents because of reduced energy gap between the S-2 and S-1 states, Delta E(S-2-S-1), as well as interaction with the solvent molecules. Occurrence of S-2-fluorescence in polar solvents, despite small energy gap, suggests that symmetry allowed S-2((1)A(1)) -> S-0 ((1)A(1)) radiative and symmetry forbidden S-2 ((1)A(1)) -> S-1 ((1)A(2)) nonradiative transitions are the factors responsible for the S2 fluorescence in MT. Lifetime of the S-2 state is shorter (varying in the range 0.28-3.5 ps in different solvents) than that predicted from the Delta E(S-2-S-1) value and this can be attributed to its flexible molecular structure, which promotes an efficient intramolecular radiationless deactivation pathways. The lifetime of the S-1 state (similar to 1.9-6.5 ps) is also very short because of small energy difference between the S-1 and T-1 states (Delta E(S-1-T-1) similar to 300 cm(-1)) in cyclohexane and hydrogen-bonding interaction as well as the presence of the isoenergetic T-1(pi pi*) state to enhance the rate of the intersystem crossing process from the S-1(n pi*) state in protic solvents.