Second-harmonic generation-circular dichroism (SHG-CD) effects in thin films of a chiral poly(3-alkylthiophene) have been investigated. Polarization patterns were recorded for several angles of incidence and analyzed using a recently developed optical model that takes all linear and non-linear optical achiral and chiral terms into account. From a complete analysis of the second-order susceptibility tensors, it is clear that SHG-CD in this particular system cannot be described by electric-dipole contributions only, but instead relies on the presence of strong magnetic-dipole contributions, similarly to linear optical CD effects. (C) 2007 Elsevier B.V. All rights reserved.