Pentoxifylline (PTX), methylxanthine derivative and phosphodiesterase inhibitor, has been in use for more than 20 years (with minimal side effects) for the potent hemorrheologic properties and was recently discovered to have influence on function of some immune cells and production of cytokines. Human and animal studies have shown that PTX therapy results in a variety of physiologic changes at the cellular level, which may be important in treating a diverse group of human afflictions. Immune modulation includes increased leukocyte deformability and chemotaxis, decreased endothelial leukocyte adhesion, decreased neutrophil degranulation and release of superoxides, decreased production of TNF-alpha and decreased NK cell activity. Potential medical uses of PTX are reviewed.