Petrols with different octane numbers, diesel fuel and solutions of cri de oil in toluene have been studied by the methods of absorption spectroscopy, circular dichroism spectroscopy and correlation spectroscopy of scattered light. Circular dichroism signal was registered for crude oil solutions in the spectral ranges corresponding to the measured earlier resonance absorption of asphaltene solutions in toluene. We show that the optical activity of crude oil solutions is due to the aggregation of asphalte to molecules in one spectral range and is intensified with the aggregation of asphaltene molecules in another spectral range. Petrols have no optical activity. The optical activity registered for diesel fuel is possibly due to the aggregation of asphaltene molecules. (c) 2006 Elsevier Inc. All rights reserved.