By definition, parasites harm their hosts. Yet substantial evidence from animal models of human disease support the hypothesis that infection with helminths can suppress the development of other maladies. Here, the view is presented that assessment of the immunophysiological response to helminths could identify that infection with specific parasites would be therapeutically useful (although many helminths could not fulfil this role) and lead to precise knowledge of the immune events following infection, to identify ways to intervene in disease processes (in the absence of infection per se) that can be used to treat, and eventually cure, inflammatory and autoimmune disease.