 A study of people with MS naturally infected with intestinal parasites did show significant protection over 5 years, and the levels of biological markers of the infection and some immune substances triggered by it were similar to the ones we obtained with controlled infection in normal volunteers, allergic and asthmatic peoples. We think the study has a genuine potential to benefit people with MS, and there is known interest in the MS patient community. At the therapeutic doses proposed here, this is an innocuous infection. Natural hookworm infection affects 1 billion people worldwide, often without symptoms unless the parasite load is very high. Our controlled exposure studies have shown good tolerability and safety; the risk of infecting others and auto-infection virtually is nil in Western standard hygiene conditions. Many people with MS when asked stated they would prefer an innocuous infection with microscopic larvae to a man-made product that may have more side effects. If the protective mechanisms are determined these studies may also lead to new ways of treating MS, possibly by selecting only the specific chemical components of the worms and the immune response to them that confer protection. 