  We investigate BBN in scalar-tensor theories of gravity with arbitrary matter
couplings and self-interaction potentials. We first consider the case of a
massless dilaton with a quadratic coupling to matter. We perform a full
numerical integration of the evolution of the scalar field and compute the
resulting light element abundances. We demonstrate in detail the importance of
particle mass thresholds on the evolution of the scalar field in a radiation
dominated universe. We also consider the simplest extension of this model
including a cosmological constant in either the Jordan or Einstein frame.
