ESb and BW-O-Li1 are T-lymphoma cell lines that form metastases in various organs after injection into syngeneic mice. In vitro, both cell lines invade through a fibroblastic monolayer, but ESb cells do so much slower than BW-O-Li1. By the use of Fourier analysis of cell outlines, we can relate this difference in invasiveness to a difference in cell motility: ESb cells do not perform any conspicuous shape change, whereas BW-O-Li1 cells are actively protruding and retracting large pseudopodia. However, the low-motile ESb cells become as motile and deformable as BW-O-Li1 cells when they have eventually invaded under a fibroblastic monolayer. This indicates that ESb cells do have inherent capability for shape change. Treatment of ESb cells with the microtubule disrupting agent nocodazole concomitantly increases their shape change intensity, and their invasion rate through fibroblast monolayers. On the contrary, the microtubule stabilizing drug taxol inhibits both motility and invasion of BW-O-Li1 cells. Our observations suggest that the microtubule network can repress invasion-bound motility of lymphoid cells.