Consistency and Phenomenology of Four-Dimensional Strings

Talk given at the 26th Workshop: ``From Superstrings to Supergravity" Erice - Sicily, 5-12 December 1992: In this talk we discuss string consistency requirements on four dimensional string models, namely the cancellation of target space duality anomalies. The analysis is explicitly performed for (hypothetical) orbifold models assuming the massless spectrum of the supersymmetric standard model. In addition, some phenomenological properties of four-dimensional strings, like the unification of the standard model gauge coupling constants and soft supersymmetry breaking parameters, are investigated.