Selection of appropriate scales of measurement is fundamental to the interpretation and understanding of river systems. Principles of hierarchy theory can be used to guide the selection of scales of measurement in stream ecological studies because hierarchy incorporates relational links between nested levels. However, the scales of measurement used in macroinvertebrate distribution studies are not cast strongly into a hierarchical context. Scales are usually nested spatially, in a logical manner, but are not accompanied by an explanation of underlying relational links among scales. We describe 2 approaches to the selection of scales of measurement that incorporate hierarchical principles. The parallel hierarchy approach uses a hierarchy of river system organization, derived from the parallel discipline of fluvial geomorphology, to identify scales of measurement that may correspond with the distribution of macroinvertebrates. The self-emergence approach circumvents any a priori imposition of scales of measurement and allows scales to self-emerge from a data set. The use of these approaches shifts focus onto the detection of levels of hierarchical organization, or holons, and may advance our understanding of river ecosystems by elucidating the way in which levels of ecological and physical organization are juxtaposed within the river system.