Reservoir geochemistry assessment has traditionally used the gas chromatogram fingerprint method and star diagrams. Recently we tested alternative techniques, such as Fourier transform infra red (FTIR) and synchronous ultra violet fluorescence (SUVF) spectroscopy to optimise the evaluation of reservoir continuities, and to characterize the geochemical evolution of oils from individual reservoirs. We used some Western Mediterranean oils to demonstrate that these independent techniques provide results that are in good agreement with each other. GC fingerprints, FTIR and SUVF spectroscopy can describe the oil characteristics and its evolution in the reservoir. We also show that some FTIR parameters can be closely related to the API degree. (C) 2004 Elsevier Ltd. All rights reserved.