The authors investigated the morphology and the elastic properties of living cultured rat liver macrophages (Kupffer cells) with an atomic force microscope (AFM). Continuous imaging and elasticity mapping of individual cells in physiological buffer was carried out for several hours without damaging the cells as judged by their persistent undisturbed morphology. Dynamic events such as protrusive activity were observed in time course. The importance of the cytoskeleton for the mechanical properties of the cell has been investigated by measuring the cell's elasticity as a function of position. Chemical disassembly of the actin network by applying 10μg/ml cytochalasin B decreased the cell's average elastic modulus seven-fold within less than 40 minutes. Treating the cells with 0.1μg/ml latrunculin A resulted in a two-fold decrease in the elastic modulus merely in the perinuclear region after 40 minutes, whereas other parts of the cell were not affected.