"Ice," the popular term for methamphetamine hydrochloride (METH), is the form of the drug now consumed by users. "Ice" is absorbed into the system after either smoking or snorting, and it is this rapid influx of drug that produces effects similar to those after intravenous administration. The intensity of METH actions in the central and peripheral nervous system shows tolerance after chronic administration, indicating that neuroadaptations have occurred. Thus, the physiological processes and corresponding biochemical mechanisms that regulate neuronal function have been changed by METH exposure. These biological alterations contribute to the craving and dependence associated with METH abuse and the withdrawal syndrome upon abstinence; however, these changes in behavior may also result from METH-induced neurotoxicity. Neurotoxicity is an adverse effect on the structure or function of the central and/or peripheral nervous system by a biological, chemical, or physical agent. This article describes the neurotoxic effects of METH on the striatal dopamine system. 3 figures and 64 references