Top: T_eff–Radius diagram for the primary star of the HD 54236A system. Middle: T_eff–Radius diagram for the secondary star of the HD 54236A system. Comparison to the Yonsei–Yale stellar evolutionary tracks (Yi et al. 2001) suggests an age for HD 54236A near the ZAMS (which occurs at an age of 300 Myr in these models) and roughly consistent with an age of 225 ± 50 Myr as determined from other age diagnostics. Bottom: H–R diagram showing all three components of the HD 54236 system (black symbols) compared to the PMS evolutionary models of Baraffe et al. (1998); shown are isochrones at ages of 1, 3, 10, 30, 100, and 300 Myr (red dashed lines) and tracks for masses of 0.6–1.2 M_⊙ in increments of 0.1 M_⊙ (blue curves).