  We present the first results of a study of the expected properties of the
first stellar generations in the Universe. In particular, we consider and
discuss a series of properties that, on the basis of the emission from
associated HII regions, permit one to discern {\it bona fide} primeval stellar
generations from the ones formed after pollution from supernova explosions. The
expected performance of NGST for the study and the characterization of
primordial sources is also discussed.
