Aspartame is one of the commonly used food additives. It was discovered that toxic concentrations of aspartame decreased the acetylcholine esterase activity in human erythrocyte membrane. We aimed in this study to evaluate the toxic effect of Aspartame on acetylcholinesterase activity, and the role of vitamin E as well as L carnitine in the protection against this toxicity. This study resulted that aspartame decreased acetylcholine esterase activity in human erythrocyte membrane, and that each of vitamin E and L carnitine protected the erythrocyte membrane against its toxicity. As a conclusion, we should restrict the use of aspartame, and use vitamin E or L carnitine to protect against its toxicity.