  We discuss charged string solutions of the effective equations of D=4
heterotic string theory with non-constant dilaton and modulus fields. The
effective action contains a generic moduli-dependent coupling function in the
gauge field kinetic term and a non-perturbative scalar potential. This is a
review of hep-th/9307123 by M. Cvetic and the author. To be published in the
Proceedings of 27-th International Symposium on Theory of Elementary Particles,
Wendisch - Rietz, September 1993.
