  We review recent results on the theta dependence of the ground-state energy
and spectrum of four-dimensional SU(N) gauge theories, where theta is the
coefficient of the CP-violating topological term F-Fdual in the Lagrangian. In
particular, we discuss the results obtained by Monte Carlo simulations of the
lattice formulation of QCD, which allow the investigation of theta dependence
around theta=0 by determining the moments of the topological charge
distribution, and their correlations with other observables. The results for
N=3 and larger values of N support the scenario obtained by general large-N
scaling arguments.
