A generalized second law in string cosmology accounts for geometric and qua
ntum entropy in addition to ordinary sources of entropy. The proposed gener
alized second law forbids singular string cosmologies, under certain condit
ions, and forces a graceful exit transition from dilaton-driven inflation b
y bounding curvature and dilaton kinetic energy, (C) 2000 Published by Else
vier Science B.V. All rights reserved.