This article presents information on the Jackson toxic milk mouse as a model for copper loading. Copper is an essential trace element required for the normal biological function of several prokaryotic and eukaryotic enzymes. Excessive production of free radicals can result in tissue damage due to oxidative stress. Recently, free radical- induced oxidative stress has been implicated in a variety of neurological disorders, including Alzheimer disease, Parkinson disease, and amyotrophic lateral sclerosis.