Ultrafast dynamics of the optically allowed S-2 (1(1)B(u)(+)) state in all-trans-carotenoids with a number of conjugated double bonds, n=7-15, has been investigated by femtosecond Kerr-gate fluorescence spectroscopy. The lifetime of the S-2 state is determined eliminating effect of excess vibrational energy. The lifetime has a maximum for n=9 and shows anomalous dependence on the energy gap between the S-2 and S-1 states. (c) 2006 Elsevier B.V. All rights reserved.