FM 97-9 Author: G. Gallavotti Title: Chaotic dynamics, fluctuations, nonequilibrium ensembles. Abstract: A review of some recent results and ideas about the expected behaviour of large chaotic systems and fluids. Keywords: Chaos, Statistical Mechanics, Nonequilibrium ensembles Giovanni Gallavotti Fisica, Universita' di Roma La Sapienza, P.le Moro 2, 00185, Roma, Italia. e-mail giovanni@ipparco.roma1.infn.it tel. 6-49914370, fax 6-4957697 Home page: http://www.math.rutgers.edu/~giovanni