Free radicals are an important weapon in the immune system, but they can also cause chemical reactions that lead to damage of fatty acids, DNA mutation, and protein destruction. This program examines how the most important radicals are created, and how they work. The relationship between chain reactions of radicals within the body and conditions such as arteriosclerosis is examined. How the antioxidants alpha-tocopherol, beta-carotene, and vitamin C protect the body from damage is demonstrated through computer animation. Connections between free-radical production and cancer, heart attack, stroke, and cataracts are suggested. (31 minutes)