Gentamicim, an aminoglycoside antibiotic, is frequently used due to its high efficacy against microorghanisms. The principal side effect of this class of antibiotics is nephrotoxicity, which may occur in up to 20% of the exposed patients. It has been shown that, the generation of free oxygen radicals in renal cortex were enhanced by Gentamicin. The efficacy of methotrexate, a widely used cytotoxic chemotherapeutic agent in ALL, is often limited by severe side effects and toxic sequelae. The significant reduction in glutathione levels promoted by methotrexate leads to a reduction of effectiveness of the antioxidant enzyme defense system, sensitizing the cells to ROS. Carbamazepine is a tricyclic antiseizure drug effective in treatment of both and generalized tonic-clonic and partial seizures. A significant reduction in glutathione (GSH) levels has been reported by carbamazepine. The present study is undertaken to determine whether taurine, a potent free radical scavenger, could ameliorate drug-induced toxicity. In 72 patients who treated by MTX, gentamicin or carbamazepin, following a routine treatment, either placebo or taurine (2g/day P.O) will be administered. Hepatotoxicity, nephrotoxicity and hemotoxicity will be studied in both groups. Six blood samples will be obtained (every 2 months). Ototoxcity in gentamicin group will be studied by odiometry.