2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/47765After a review of some topics concerning the phenomenological applications of perturbative string theory, I discuss to what extent all of it is affected by the recent developements in string dualities.35 pages, LaTex . Minor corrections. References added. To appear in the proceedings of the Workshop on Phenomenological Applications of String Theory (PAST), ICTP, Trieste (Italy), October 1997High Energy Physics - PhenomenologyHigh Energy Physics - Theorytext