Three putative shorelines first proposed by Parker et al. <1989> are topographically and morphologically evaluated within a 700,000 km2 study area in northern Arabia Terra, Mars. Results are consistent with a shoreline interpretation for the Arabia and Deuteronilus contacts but do not support the proposed Acidalia shoreline. The Arabia contact follows an equipotential surface with a mean elevation of -3707 m and a mean deviation of ¿13 m. For Deuteronilus, results suggest that the originally proposed shoreline represents two distinct, regional shorelines, because two separate portions of the original Deuteronilus contact approximate equipotential surfaces of -4200 m ¿ 5 m and -4000 m ¿ 6 m. For both the Deuteronilus and Arabia contacts, there is geomorphic evidence for erosion, and some landforms are similar to analogous terrestrial coastal landforms. These results permit, but do not prove, the past existence of an ocean ponded within the northern lowlands, possibly as recently as the Amazonian.