Spectral type vs. T _eff for the pre-MS (solid black line) and dwarf (solid gray line) T _eff scales derived in this work. For comparison we plot the giant T _eff scale of van Belle et al. (1999) (dotted line) and the T _eff scale of Luhman et al. (2003) (dashed line), appropriate for ~1 Myr old stars. Our pre-MS T _eff scale is within 100 K of the dwarf scale as a function of spectral type, except for spectral types G5 through K6, which are ~250 K cooler than their MS counterparts.