Geomorphic analyses and crater statistics indicate the distribution of materials on the east rim (27.5°–42.5° S, 260°–275° W) of the Hellas basin and constrain the timing, nature, and interactions of geologic processes which have modified the Hellas region. The discernible geologic history of the area began with the formation of the impact basin and the emplacement of highlands that became heavily cratered during the Noachian Period. The tectonic setting of the region was established at this time, and basin structures promoted and influenced subsequent volcanic, tectonic, and fluvial activity. Degradation of the highland units by fluvial, mass-wasting, and aeolian processes began in the Noachian and continued into the Hesperian and Amazonian Periods. Sedimentary plains covered low-lying regions of the highlands; their pitted surfaces in some areas suggest subsidence and the presence of volatiles. Emplacement of lobate debris aprons, shed from highland peaks and possibly facilitated by ice creep, occurred in the Amazonian Period. The volcanic history of the east rim of the Hellas basin began with the formation of the highland paterae. The low, dissected shields of Hadriaca and Tyrrhena Paterae formed in the Late Noachian or Early Hesperian Epochs and are older than or coeval with the ridged plains of Hesperia Planum. Volcanic activity continued throughout the Hesperian Period with the emplacement of the caldera-filling materials at Hadriaca Patera and the lava flows of the flank flow unit of Tyrrhena Patera. Outflow channels and related channeled plains of the Hesperian and Amazonian Periods suggest an extensive and complex history of volatile-driven erosion and sedimentary deposition. Dao and Harmahkis Valles are interpreted to be collapsed regions of the older plains; a combination of surface and subsurface flow has removed materials with deposition on the floor of the Hellas basin. The geologic evolution of the region, determined from the observed surface morphology and stratigraphic relationships and refined by crater statistics, indicates that a combination of diverse geologic processes acted in the degradation of the Hellas basin. The effects of volcanism and volatile-driven processes were prominent throughout the Hesperian and well into the Amazonian Periods. The proposed transition from explosive to effusive volcanism in the Hellas region is supported by the relative ages indicated by crater statistics. The heat released by volcanism may have resulted in the melting of ground ice and contributed to the development of the channeled plains and outflow channels. The presence of wrinkle ridges on units that are inferred to be relatively young from their crater size-frequency distributions suggests deformation in the Late Hesperian or Early Amazonian Epoch.