  We review recent measurements of high transverse momentum (high $p_T$) hadron
production in nuclear collisions by the STAR Collaboration at RHIC. The
previously observed suppression in central Au+Au collisions has been extended
to much higher $p_T$. New measurements from d+Au collisions are presented which
help disentangle the mechanisms responsible for the suppression. Inclusive
single hadron spectra are enhanced in d+Au relative to p+p, while two-particle
azimuthal distributions are observed to be similar in p+p, d+Au and peripheral
Au+Au collisions. The large suppression of inclusive hadron production and
absence of the away-side jet-like correlations in central Au+Au collisions are
shown to be due to interactions of the jets with the very dense medium produced
in these collisions.
