  Non-perturbative studies of the thermodynamics of strongly interacting
elementary particles within the context of lattice regularized QCD are being
reviewed. After a short introduction into thermal QCD on the lattice we report
on the present status of investigations of bulk properties. In particular, we
discuss the present knowledge of the phase diagram including recent
developments of QCD at non-zero baryon number density. We continue with the
results obtained so far for the transition temperature as well as the
temperature dependence of energy and pressure and comment on screening and the
heavy quark free energies. A major section is devoted to the discussion of
thermal modifications of hadron properties, taking special account of recent
progress through the use of the maximum entropy method.
