Polygonally shaped epithelial lens cells show elongation upon subculturing. As a result cytoskeletal structures change in relative abundancy. A cytoskeletal constituent, occurring in the perinuclear part of the cytoplasm of the polygonal cells gradually disappears, while stress fibers (actin bundles) assemble and become especially pronounced in elongated cells. After treatment with cytochalasin B (CB) the cells attain an arborized shape, a process which is reversible only for young cells. In contrast, elongated cells do not return to their initial shape after removal of CB. These results strongly suggest an important role of microfilaments in lens cell elongation at least in vitro.