High-energy nuclear collisions at the Relativistic Heavy Ion Collider are used to create a hot, dense QCD medium, likely a deconfined Quark-Gluon Plasma, and study its properties. High-pt partons are produced in the early stage of the collision and lose energy through gluon radiation and elastic scattering while propagating through the medium. I will review experimental measurements of high-pt hadron production at RHIC and compare to model calculations to explore which aspects of the basic QCD parton energy loss process are experimentally accessible. In the outlook, I will discuss how new measurements using photons and full jet reconstruction to directly access the underlying parton energies will provide more insight in the energy loss process and the nature of the QCD matter produced at RHIC as well as at the LHC.