Several previous studies have demonstrated a beneficial effect of the adenosine receptor (AdoR) antagonist theophylline in different forms of acute renal failure in laboratory animals and in humans. Therefore, we wanted to test whether theophylline can also improve impaired allograft function following ischemia reperfusion injury in experimental kidney transplantation (KT). Orthotopic transplantation of the left kidney was performed from Fisher 344 into Lewis rats. All transplanted rats received daily cyclosporine (5 mg/kg). The effect of theophylline treatment (10 mg/kg) on graft function was compared with appropriate controls on day 5 after KT by assessment of glomerular filtration rate (GFR) (inulin clearance). On day 5, GFR of allografts in control rats was 0.23 Ϯ 0.05 ml/min/g kidney weight (n ϭ 10) compared with 0.50 Ϯ 0.09 ml/min/g in rats receiving