Pentoxifylline (PTX) is a nonselective phosphodiesterase inhibitor that inhibits the production of TNF alpha and IL6 and IL-10 cytokines. In renal rejection TNFa, IL-6, and IL-10 may have important roles. In this study, 22 renal transplant recipients treated with tacrolimus, prednisolone, and mycophenolate mofetil were prescribed PTX (2 X 600 mg/d) for 3 months (GI), and 20 similar patients not receiving PTX were used as controls (GII). Stable subjects whose serum creatinine was lower than 1.8 mg/dL and were more than 6 months posttransplant, were enrolled into this study if the blood pressure was well controlled and there was no diabetes mellitus, infection, or inflammation. At the end of 3 months TNF-alpha decreased from 4.2 +/- 2.1 to 2.4 +/- 0.7 (P = .001) and 4.0 +/- 2.2 to 3.9 +/- 1.7 (P = .718), IL-10 also decreased from 3.90 +/- 1.9 to 2.38 +/- 0.6 (P = .001) and 4.02 +/- 1.6 to 3.82 +/- 1.5 (P = .225) in GI and GII, respectively. For IL-10 and TNF-a the alterations between baseline and the last visit of GI and GII were significant (P < .002 for all). Resistive index (RI) decreased in GI but the difference in alterations between baseline and the last visit of GI and GII was marginal.