We analyze the status of numerical simulation of QCD at finite temperature. Emphasis is put on quantitative predictions emerging from lattice calculations that may be tested in heavy ion experiments. Recent results on the chiral phase transition, thermodynamics of the quark gluon plasma phase and various screening lengths are discussed. Presented at the 6th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions-Quark Matter 1987, 24–28 August 1987, Nordkirchen, Federal Republic of Germany.