The principle of allometric growth was first developed by biologists, and states that the ratio of the relative growth rate of an organ to that of the whole organism remains constant. Allometric relations in biology are identical with the power-function relations found in all empirical sciences. The instances of allometric growth in geomorphology so far suggested are n i fact examples of size-related allometric relations, and not of allometric growth relations. Data from an experimental study of drainage network evolution did not support the concept of allometric growth, and a brief theoretical survey suggests that there is no reason to expect that river systems should exhibit allometric growth.