  We study massive spin-1/2 fermion production in nonsingular superstring
cosmology, taking into account one-loop quantum corrections to a superstring
effective action with dilaton and modulus fields. While no creation occurs in
the massless limit, massive fermions can be produced by the existence of a
time-dependent frequency. Due to the increase of the Hubble expansion rate
during the modulus-driven phase, the occupation of number of fermions continues
to grow until the point of the graceful exit, after which fermion creation
ceases with the decrease of the Hubble rate.
