The efficiency of second-harmonic generation from chiral surfaces and thin films ii; different for left- and right-hand circularly-polarized fundamental light. Such optical activity can occur in the electric-dipole approximation. However, to explain our results for chiral polymer films, magnetic contributions to the nonlinearity must be included. A technique that uses a quarterwave plate to continuously vary the polarization of the fundamental beam was used to determine the relative complex values of the components of the tensors that characterize the nonlinear interaction. The largest magnetic components were similar to 20% of the largest electric components. Second-harmonic generation from achiral anisotropic surfaces tan also lead to optical activity. This occurs if the orientation of the anisotropic sample mal;es an otherwise achiral experimental arrangement chiral, The effect occurs in the electric-dipole approximation and changes sign as the handedness of the setup is reversed, (C) 1998 Elsevier Science B.V.