Outstanding Issues on Pulsations in Young Stars

We briefly summarize the impact of protostellar evolution on the initialconditions of pre-main-sequence (PMS) contraction and identifytwo different kinds of instability in young stars closely connected to thePMS physical conditions. These are the Scuti type pulsations in intermediate-mass PMS stars (Herbig Ae stars) and the pulsation instability of brown dwarfs and very low mass stars. For the former, we review recentobservational and theoretical work and provide the location in the H-Rdiagram of known candidates. For the latter, the possibility that deuteriumcan be an efficient driving mechanism of the instability is explored.