Digital elevation data have been obtained for 54 open rock basins from aerial diapositives using an analytical stereoplotter. The term "open rock basin" is used to distinguish these basins from the closed rock basins of classical glacial cirques. Whereas closed basin cirques have been subjected to considerable morphometric analysis, open rock basins, which are equally prevalent in mountain environments, have not. The morphometric analyses in this paper are based on nine indices: length, width, area, relief, length/width, length/relief, width/relief, area/relief, and compactness. Cluster analysis of compactness and area/relief data indicates five distinct clusters of open rock basins, which are attributed to variations in topoclimate and geologic structure. The three largest clusters are labelled rockfall chutes, rockfall funnels, and open cirques. The cirque cluster is compared with glacial cirques for which published morphometric data exist. Comparable length/width ratios suggest an equilibrium in rock basin planimetric shape. However, the considerably greater relief and lower area/relief values of the open cirques suggest that glaciation of these rock basins has been limited to their upper reaches in the form of niche glaciers.