Stimulated Brillouin scattering in various liquids is examined in a transverse resonator and in a backward-wave oscillator. Comparison with elementary resonator theory indicates that the data are in satisfactory agreement for many liquids. The theoretical picture for the unstable backward-wave configuration is complicated by phonon transit-time effects, but even here the results establish guidelines for the theory. It is found necessary to discard the results for some liquids because of self-focusing and other nonlinear processes which interfere with the Brillouin effect.