The present study aimed to investigate the protective effect of Spirulina platensis (SP) on gentamicin sulphate (GS)-induced changes in the levels of lipid peroxidation and endogenous antioxidants in the kidney of rats. Sprague-Dawley rats were treated in separate groups as follows for 7 consecutive days: control (C), gentamicin sulphate (100 mg/kg i.p.) (GS), Spirulina platensis (1000 mg/kg orally) (SP) and Spirulina platensis (1000 mg/kg orally) plus gentamicin sulphate (100 mg/kg i.p.) (SP + GS). The degree of protection was evaluated by determining the effects of Spirulina platensis on malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPX) and nitric oxide (NO), and plasma creatinine and urea levels were estimated in kidney homogenates to evaluate antioxidant activity, and the kidney was histologically examined as well. Spirulina platensis elicited significant nephroprotective activity by decreasing lipid peroxidation (MDA) and elevated the levels of GSH, SOD, GPX, NO, creatinine and urea. Furthermore, these biochemical observations were supplemented by histological examination of the rat kidneys. In conclusion, the present study indicates a very important role of reactive oxygen species (ROS) and the relation to renal dysfunction and point to the therapeutic potential of Spirulina platensis in gentamicin sulphate induced nephrotoxicity. Copyright (C) 2008 John Wiley & Sons, Ltd.