2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/5778A reliable method for estimating the black-hole masses of high-redshift quasars would provide crucial new information for understanding the nature and cosmological evolution of quasars. In this proceedings we summarize the results of our recent paper (McLure & Jarvis 2002) which provides a virial black-hole mass estimator based on rest-frame UV observables, thereby allowing reliable black-hole mass estimates to be obtained out to redshifts of $z\sim2.5$ from optical spectra alone.5 pages, 3 figures, To appear in "Carnegie Observatories Astrophysics Series, Vol. 1: Coevolution of Black Holes and Galaxies," ed. L. C. Ho (Pasadena: Carnegie Observatories, http://www.ociw.edu/ociw/symposia/series/symposium1/proceedings.html)Astrophysicstext