A review of finite temperature lattice calculations for quantum chromodynamics is given. We show how the thermodynamic quantities can be evaluated by Monte Carlo methods, once finite temperature field theory has been formulated on a lattice. The existing results for chemical potential zero and in quenched approximation are discussed. They exhibit a clear first order transition for SU(3) lattice QCD and probably a second order transition for SU(2) lattice QCD. The chiral and deconfinement transitions are coinciding in the quenched approximation.