Immunotherapy began in 1774 when the Dorset farmer Benjamin Jesty inoculated his wife and two sons with the pus from the teat of a cow suffering from cow pox, using his wife's knitting needle as a vaccinating implement. It has made slow progress. Meanwhile the science of Immunology has burgeoned so much that if all immunologists read every page of the Journal of Immunology, let alone the other Immunology journals, then they would have no time left to write for it. I am pleased that some of them have found the time to write for this volume. In spite of the rapid expansion in immuno­ logical knowledge and the undreamt of complexity of the immune system that has been unravelled, immunologists have remained until recently erudite but therapeutically effete. Indeed anyone purporting to treat disease by immuno­ logical methods has been in danger of being labelled a quack or a crackpot. Happily things are changing. The nine chapters of this volume detail nine quite different approaches to manipulating the immune system for therapeutic benefit. All are experimental and they have been attended with greater or lesser degrees of success. In some cases their main effect has been to elucidate the complexity of the problem. On the other hand, there are people alive and well today as a result of these approaches who would otherwise have perished. Immunotherapy is here to stay and it can only get better.