Clinical research has brought great progress in our understanding of the mechanisms by which chronic inflammatory and degenerative diseases damage tissues and organs. Unfortunately there has been little advance in our knowledge of the insults which initiate these processes. Thus much of our treatment for chronic disorders remains palliative. The principal therapeutic triumphs in medicine have followed the identification of microbial infections for which specific remedies have been devised either from chance observation or from the painstaking efforts of the pharmaceutical companies. Since there have been few clues to the causes of most chronic inflammatory disorders, speculation on this subject has flourished without restraint.