“Striations” produced by catastrophic subglacial drainage of an ice-dammed lake were investigated in front of Mjelkedalsbreen, Jotunheimen, southern Norway. At each site, length, width, and orientation of at least 50 “striations” were recorded. These data are compared with similar measurements from a glacially abraded “control” site. On the basis of length or width measurements alone, “striations” produced by subglacial drainage are not consistently distinguishable from those produced by glacial abrasion. However, the former display more variable orientations and cross-cutting relationships which could be misinterpreted as indicating changing ice-flow directions. They can be recognized by the occurrence of some “striations” with relatively low length : width ratios, which indicate the transport of boulders by saltation.