  We study the scaling behavior of the 4D SU(3) lattice gauge theory in the
presence of a theta term, by Monte Carlo simulations computing the topological
properties at imaginary theta. The numerical results provide a good evidence of
scaling in the continuum limit. The imaginary theta dependence of the
ground-state energy turns out to be well described by the first few terms of
related expansions around theta=0, providing accurate estimates of the first
few coefficients, up to O(theta^6).
