Abstract: An approach based on the graph theory was used to study the Pitzer acentric factor of paraffins. Wiener Number was found to be a good measure of acentric degree of molecular structure. A proportional relationship between Pit-zer acentric factor and Wiener Number for paraffins was established. The relationship can be used to predict Pitzer acentric factor of isomeric alkanes. The predicted results agreed with experimental values satisfactorily.