Low-level, steady electric fields (6-10 volts/cm) stimulated cultured corneal stromal fibroblasts to undergo directional orientation and translocation. The orientative movements (galvanotropism) consisted of somatic elongation of the cells into spindle shapes along an imaginary axis perpendicular to the field; the cathodal edge of the cell underwent retraction, while the anodal edge and the longitudinal ends developed ruffled membranes and lamellipodia. The translocational movements (galvanotaxis) consisted of directed migration of the cells towards the anode. While most actin-containing stress fibers became aligned along the long axes of the elongated fibroblasts (with distal ends of the stress fibers terminating at the longitudinal extremes of the cells), some were aligned towards the anodal direction (with distal terminations inside ruffled membranes and lamellipodia on the leading anodal edge of cells). The distal ends of stress fibers were associated with discrete foci of vinculin, ie, focal indicators of cell-to-substrate adhesion; these foci were abundant at the longitudinal ends and at the anodal edge of the elongated cells. The observed cytoskeletal changes are consistent with an active, rather than passive, directed migration of stromal fibroblasts in response to constant electric fields.