We computed a set of pre-main sequence models using the YREC evolution code to study delta Scuti pulsations of PMS stars, focusing on their non-adiabatic properties and the region of instability in the H-R diagram. The properties of the radial ( = 0) modes on the early pre-main sequence are very similar to those on the late post-main sequence, with slightly shorter periods corresponding to smaller radii. The period ratio 1/0 lies at low values of 0.5 near the base of the Hayashi track, but rapidly rises to values near 0.77 typical of delta Scuti stars once the stellar models move closer to the ZAMS. We find unstable models (E/E>0) on the pre-main sequence for all models between 1.5 and 4.0 solar masses, though at the high-mass end, the fundamental blue edge is reached very early in the pre-main sequence lifetime. The slope of the pre-main sequence blue edge appears to overlap the edge for the main- and post-main sequence stars. We also tested models for V346 Ori similar to those described in Pinhiero et al. (IAU Colloq. 185, 2001), and find that while V346 Ori almost certainly lies near the ZAMS, it is uncertain whether it is a pre-main sequence star.

 
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