Humic substances extracted from soils in loessial area where the annual precipitation and evaporation ranged from 340-800 mm and 720-2500 mm respectively were investigated by elemental analysis, x-ray diffraction, paper electrophoresis and infra-red spectrophotometry. Results obtained showed that the aromaticity and mobility of humic acid varied regularly with climatic conditions under which the soils formed. The drier the climatic conditions under which the soils formed, the higher aromaticity and lower mobility of humic acid. Among the humic acid of the soils studied, that extracted from ortho loessial soil had the highest aromaticity and the lowest mobility, while that extraded from yellow cinnamon loessial soil had the lowest aromaticity and the highest mobility.