  Observations of binaries have traditionally provided the means for
ascertaining stellar masses. Here, we use the published data on 8
pre-main-sequence pairs to gauge the accuracy of our own, recently calculated,
evolutionary tracks (Palla & Stahler 1999). We consider both eclipsing,
double-lined spectroscopic binaries, which provide the mass of each star
separately, and non-eclipsing, double-lined systems, which yield only the
ratio. We also analyze the visual, quadruple system GG Tau, for which the sum
of the two component masses follows from observations of the circumbinary disk.
  In almost all cases, our theoretically derived masses or mass ratios are in
good agreement with the empirical values. For two binaries (NTTS 162814-2427
and P1540), the observational results are still too uncertain for a proper
comparison. We also find that the derived contraction ages within each
pre-main-sequence pair are nearly equal. This result extends earlier findings
regarding visual pairs, and indicates that the components of all binaries form
in proximity, perhaps within the same dense cloud core. Finally, our study
reveals that the Trapezium star BM Ori is very young, since both the star
itself and its companion have contraction ages less than 10^5 years.
