Free radical reactions occur in the environment (e.g., ozone depletion), in the body, (e.g., aging) and in the scientistıs lab. They are often damaging to the system they are generated in and research is underway to decrease or halt any damaging effects. In the field of drug addiction there is a wealth of research being conducted to understand the brain mechanisms responsible for repeated administration. This is done in order to find a treatment for the addict. Methampetamine is a drug of abuse which is also a neurotoxin because it aids in the production of free radicals. These free radicals damage striatal tissue by oxidizing the lipids. Thus, the ability to model the concentrations of metabolites and intermediates will give additional insight to the mechanisms occurring in the brain. In this model, substrate A2 generates free radical A. Radical A reacts with neutral compound BH to form free radical B along with product AH. This free radical B reacts with another substrate A2 to regenerate the first free radical A and product AB. This chain process continues until the concentration of A2 is depleted. Although the rates of these reactions change depending on the system being described, STELLA can be used to model these reactions whether they occur in solution, the environment, or the body.