Fifty-one oils from ten fields in the Western Niger Delta were anolyzed for their C-7 hydrocarbon contents. Hierarchical Cluster Analysis and Principal Component Analysis were used to discriminate the oils into four sets which were distinct in all the seven variables used in the cluster analysis. Methylcyclohexane and toluene were the most important discriminating variables. In spite of this separation into four sets, all the oils were found to exhibit a high six-ring preference (6RP). The distribution of C-7 hydrocarbons in the oils indicated that two of the eleven fields are homogenous in terms of oil type, whereas the rest are not.