The manner of locomotion of Schwann cells during normal development was studied by means of repeated observations and photomicrographs of individual cells at closely spaced time intervals and focal levels. In developing tadpole peripheral nerves, Schwann cells move sporadically with brief periods of rapid translation of the whole cell interspersed with longer intervals when the cell shows little or no overall movement. Highest rates of locomotion averaged 5 micrometer/minute with a duration of no greater than four to six minutes. Net rates of speed measured over at least 20 minutes were always considerably lower, with the average being 1.9 micrometer/minute. Rapid locomotion involves protrusion and growth of several pseudopodia, while the cell body remains in place, followed by attachment of these processes to an axonal surface, and finally detachment of the trailing portions of the cell as the entire cell hitches forward, "inchworm-style".