Recent progresses in the study of jet modification inhot medium and their consequences in high-energy heavy-ioncollisions are reviewed. In particular, I will discuss energy lossfor propagating heavy quarks and the resulting modifiedfragmentation function. Medium modification of the parton fragmentation function due to quark recombination are formulated within finite temperature field theory and their implication onthe search for deconfined quark-gluon plasma is also discussed.
