Lyme Borreliosis is a worldwide infectious disease causing a multisystem illness with considerable morbidity, particularly in North America and Europe. The causative agent is the spirochaete Borrelia burgdorferi, which is usually transmitted by the ixodid tick from animal reservoirs. This book is formed by contributions from the Second European Symposium on Lyme Borreliosis, held at St George’s Hospital Medical School, London in 1993, which reviewed the current state of knowledge of the condition with regard to clinical manifestations, diagnosis, treatment, ecology, epidemiology, biology and immunopathogenesis. In this book, important data is reviewed concerning the clinical manifestations of Lyme Borreliosis. It seems that strain variation of the spirochaete is the main cause of regional differences seen in the clinical presentation of patients. One striking example of this, is the relatively high incidence of Lyme arthritis in the USA and apparent rarity of this manifestion in some areas of Europe. These important studies open the way for exciting new research that focuses on the immunological and molecular mechanisms that result in disease. A full insight into the ecology of Borrelia burgdorferi is essential to a balanced understanding of the disease and a number of excellent reviews on this subject are included. Significant advances with regard to the biology of Borrelia burgdorjeri and the immunopathogenic mechanisms that result in disease have been made, enabling the role of the Band T lymphocytes in disease to be established and the development of sophisticated phenotyping methods, improved diagnostic tests and effective vaccines.