This is an exciting era in medicine and in science. Successive waves of advance in knowledge gather, break and recede uncovering fresh challenges and new opportunities. Each plays its part in eroding the tidemark of yesterday's ignorance. Many involved in the day-to-day management of patients, ill­ prepared and ill-equipped by the training which they received as under­ graduate students, find it difficult to retain contact with the advances in medical science and feel uncomfortable on the shifting sands of uncertainty upon which we now stand. Which of the new ideas is sound ? Upon which data may we rely? How may we distinguish the real from the unreal, the true from the false, recent advances from recent retreats? These are the anxieties, often either unstated or alternatively expressed in terms of an attitude of total opposition to 'all of this research rubbish' which are widespread in medical circles today. It is for these individuals who are not themselves directly involved in the immunology of rheumatic diseases but who, nevertheless, recognize the importance of this subject to their patients and, in particular, to tomorrow's patients, that this book has been written. There are two points that I believe to be of central concern. Firstly, I think it important to recognize that the intellectual basis of most of the research work being generated today is actually extremely simple.