The classical method of dividing crude oil into narrow molecular-weight cuts—distillation—is not practical in the high-boiling region. Thus, gel permeation chromatography was evaluated as a technique for characterizing the high-molecular-weight portion of crude oils. Crude oils, stripped to 180[ddot]C, were separated in a dual-column GPC system. The fractions obtained provided information concerning the amounts of material with molecular weights between 400 and 3000. Gross estimates were made of the proportion of ring and nonrmg carbons in these fractions. The latter estimates were obtained by relating molecular weights determined on the fractions to a calibration plot made up from data on model compounds.