Cisplatin is an effective chemotherapeutic agent used in the treatment of a wide array of both pediatric and adult malignancies. Dose-dependent and cumulative nephrotoxicity is the major toxicity of this compound, sometimes requiring a reduction in dose or discontinuation of treatment. Recent evidences have implicated oxidative and nitrosative stress in cisplatin-induced nephrotoxicity. Spirulina fusiformis, blue-green algae, is claimed to be a potential antioxidant. The present study was designed to explore the renoprotective potential of Spirulina fusiformis against cisplatin-induced oxidative stress and renal dysfunction. Spirulina fusiformis (500,1000,1500 mg/kg(-1) p.o.) was administered 2 days before and until 3 days after cisplatin challenge (5 mg/kg(-1) i.p.). Renal injury was assessed by measuring serum creatinine, blood urea nitrogen, creatinine and urea clearance, and serum nitrite levels. Renal oxidative stress was determined by renal TBARS levels, reduced glutathione levels, and by enzymatic activity of superoxide dismutase and catalase. A single dose of cisplatin produced marked renal oxidative and nitrosative stress and significantly deranged renal functions. Chronic Spirulina fusiformis treatment significantly and dose-dependently restored renal functions, reduced lipid peroxidation, and enhanced reduced glutathione levels, superoxide dismutase, and catalase activities. The results of the present study clearly demonstrate the pivotal role of reactive oxygen species and their relation to renal dysfunction and point to the therapeutic potential of Spirulina fusiformis in cisplatin-induced nephrotoxicity.