The use of chiral harmonophores in second harmonic generation (SHG) microscopy of lipid bilayers should enable one to obtain a signal even when the distribution of the chromophores is centrosymmetric. In order to determine optimal chiral molecules, we performed polarization-resolved second harmonic reflection experiments. We found that chirality must arise from an excitonic coupling rather than from an asymmetric center. We selectively labeled giant unilamellar lipid vesicles and cell membranes with such a molecule, namely an acridine substituted Tröger's base, as demonstrated by two-photon-excited fluorescence microscopy. We performed preliminary SHG microscopy experiments, but the poor efficiency of the current form of our molecule does not allow us to demonstrate chirality effects. © (2003) COPYRIGHT SPIE--The International Society for Optical Engineering