Humic acid from oil shale has been extracted by two procedures, and two samples were obtained. Their yield, elemental analyses, acidity, infrared spectra, u.v.-visible spectra, X-ray diffraction and the pK a values for each sample were studied. It has been found that chemical and structural changes took place upon using different extraction procedures, and that oil shale humic acid may have a similar origin to soil humic acids extracted from Jordanian soils. Based on the pK a value study, oil shale humic acids were treated as tribasic acids. This led to good agreement with the previous conclusions that there are two types of carboxylic groups in addition to a phenolic group.