Suramin is a polysulfonated naphthylurea originally designed as a treatment for trypanosomiasis; but that has also been used to treat rodent models of fulminant hepatic failure and focal brain ischemia. In this study, we determined the effects of suramin on renal ischemia/reperfusion-induced acute kidney injury in mice, in particular its effect when administered after renal injury has been established. Increasing concentrations of suramin were given 24 hours following reperfusion, a time when serum creatinine levels were at their highest level. This treatment improved renal function, as evidenced by decreased blood urea nitrogen and serum creatinine to control values and diminished histopathologic tubular damage. Suramin-treated animals had a significant reduction in apoptotic tubular cells and infiltrating leukocytes. There was also an increase of proliferating tubular cells following reperfusion compared to the number found in untreated animals. Our study shows that suramin promotes the recovery of renal function and has effective therapeutic applications when given after the occurrence of renal injury.