Femtosecond transient absorption spectroscopy was used to study the excited-state dynamics of the S2 (1(l)B(u)) state all-trans-1,3,5,7-octatetraene in solution. The sample was excited at 267 nm and probed at eleven different wavelengths from 340 to 540 nm. Combined with the picosecond fluorescence spectroscopy, this study allows direct observation of the initial excited-state dynamics of all-trans- 1,3,5,7-octatetraene and the subsequent relaxation process to the ground state. Transient absorption signals decaying on time scales of about 0.4 ps were seen at wavelengths longer than 480 nm. These absorptions are assigned to an S-n-S-2 transition, indicating that internal conversion from the S2 to SI state takes place on a 400-fs time scale. The transient absorption signals observed at shorter wavelengths, which correspond to the S-n-S-l transition, decay on a picosecond to subnanosecond time scale. A weak fluorescence at about 300-350 nm, originating from the S-2 state, and a strong fluorescence at about 350-500 nm, from the S-1 state, were observed. The time profile of the S2 fluorescence signal is almost equal to the instrument response function, and the lifetime is estimated to be faster than 5 ps, This observation is consistent with the results of transient absorption signals. The SI fluorescence signal consists of two decay components. The average lifetimes are 0.88 ns in acetonitrile and 2.0 ns in n-hexane. Nonexponential decay of the fluorescence may result from an equilibrium mixture of the fluorescent state and the conformationally relaxed state. The fluorescence intensity ratio of St to S1 in solution is much different from that observed in the gas phase. This means that the efficiency of internal conversion increases significantly in solution because of the solute-solvent interactions that are absent in the gas phase. We discuss differences in the excited-state dynamics between l,3,5-hexatriene and 1,3,5,7-octatetraene.