To determine differences in the localization and dynamics of the BcR and the actin cytoskeleton in resting CLL cells and after activation, CLL cells were seeded on poly-L-lysine–coated glass, then left either inactivated or activated with F(ab′)2 Fragment anti-IgM or anti-IgG for 5, 15, and 40 min. Here, BCR is linked to B-cell chronic lymphocytic leukemia.