The groundwater-sapping process generates peculiar landform features, including amphitheater channel head, U-shaped cross section with steep wall and flat floor, and short stubby tributaries. However, previous attempts to quantify this landform were primarily limited to the planform geometry of the channel networks and the network topology. The elevation or relief information, which is more revealing of the processes that gave rise to the landform, has not received enough attention in the literature. The hypsometric curve (area-altitude relation) combines area and relief elegantly. By treating the hypsometric curve as a probability distribution, one can quantitatively distinguish small differences in the shape of the curve (and thus in the characteristics of the landform) on the basis of hypsometric integral, the skewness and kurtosis of the curve, and the skewness and kurtosis of its density function. Preliminary results of applying this technique within an automated Geographic Information System (GIS) environment to typical terrestrial sapping landforms show that they are characterized by high hypsometric integral, low hypsometric skewness, negative density skewness, and high density kurtosis as compared with typical fluvial landforms in humid regions. Statistical analyses indicate that the differences on these hypsometric attributes between typical sapping and typical terrestrial fluvial landforms are statistically significant. Thus the hypsometric analysis technique and hypsometric attributes can be used to quantify landforms. This technique, along with other lines of evidence, can be applied to help identify the origin of landforms on other planets such as Mars, where groundwater-sapping is thought to have played an important role in its landform evolution. ¿ 2000 American Geophysical Union