  The status of lattice QCD investigations at high temperature is reviewed.
After a short introduction into thermal QCD on the lattice we report on the
present understanding of the phase diagram and the equation of state, in
particular in presence of dynamical quarks. We continue with a discussion of
various screening lengths in the plasma phase including results from
dimensionally reduced QCD. This is followed by summarizing lattice data on
quark number susceptibilities and spectral densities, both of which are of
immediate relevance to the interpretation of heavy ion experiments. A major
section is devoted to presenting simulations of QCD at small yet
phenomenologically important values for the baryon density.

High Energy Physics - Phenomenology