Impaired mononuclear leucocyte (MNL) motility can be found both in vascular and autoimmune diseases. Pentoxifylline (PTX) has a well-known therapeutic effect in vascular diseases, which is based on the rearrangement of blood cell cytoskeleton and thus increased microcirculatory flow. Most data on PTX concern red blood cells and granulocytes so now the effect of PTX on previously decreased MNL migration and chemotaxis was investigated in vitro. The results of MNL chemotaxis studies described here suggest that this drug enhances impaired MNL motility in obliterative atherosclerosis and systemic lupus erythematosus and thus may also be introduced in the treatment of certain polysystemic autoimmune diseases with decreased in vitro MNL chemotaxis.