The theory of Dirichlet forms has witnessed recently somevery important developments both in theoretical foundationsand in applications (stochasticprocesses, quantum fieldtheory, composite materials,...). It was therefore felttimely to have on this subject a CIME school, in whichleading experts in the field would present both the basicfoundations of the theory and some of the recentapplications. The six courses covered the basic theory andapplications to:- Stochastic processes and potential theory (M. Fukushimaand M. Roeckner)- Regularity problems for solutions to elliptic equations ingeneral domains (E. Fabes and C. Kenig)- Hypercontractivity of semigroups, logarithmic Sobolevinequalities and relation to statistical mechanics (L. Grossand D. Stroock).The School had a constant and active participation of youngresearchers, both from Italy and abroad.