Background and purpose: Contrast-induced nephropathy (CN) is one of the most common causes of iatrogenic acute renal failure. In fact CN is the third leading cause of new ARF in hospitalized patients. Radiocontrast-associated ARF is a significant problem in patients with cardiovascular disease. The risk factors for cardiovascular disease also predispose these patients to an increased risk of renal failure. Various strategies have been suggested for preventing CN. Since adenosine may play a role in pathogenesis of CN, theophylline, an adenosine receptor antagonist, has been investigated as a means to reduce the risk of this complication.Materials and Methods: The effects of oral theophylline (200 mg b.d) & placebo (b.d) 24 h before and for 48h after coronary artery angiography were studies on serum Cr, BUN, Na+, K+ & GFR of 70 high risk patients for CN whom were divided into two equal groups. All patients were hydrated well. Results: No differences were observed in average serum Cr, BUN, Na+, K+& GFR before angiography between the two groups. After angiography, the average serum Cr, BUN, Na+& K+ did not also change significantly in either groups, however, the changes of average GFR was different in two groups.Following angiography, patients in the theophylline group had no significant change in average GFR (83.01±26.73 vs 81.36±24.91 Ml/min), but patients in the control group showed a statistically significant fall in average GFR (86.10±34.88 VS 80.70±30.43 ml/min) (P<0.05).Conclusion: Although. in our study we had no significant raise in Cr and contrast-induced nephropathy, but since the average GFR fall significantly in control group, in contrast to case group; we concluded that theophylline prevents from some changes in renal function which produced by high osmolality contrast agents, and may have some degree of benefits to reducing CN in high risk patients.