This text discusses the current state of knowledge about Lyme disease, including its more controversial aspects. Four case studies are used to illustrate the varying course of the disease in different individuals and under different circumstances. A fifth patient is used a model for people who, despite the absence of a clear medical diagnosis, remain convinced that Lyme disease explains their symptoms. The text explains how Lyme disease is spread, who is at risk, and describes the symptoms and consequences - from the rash following a tick bite to serious complications, such as infection of the nervous system, joints and heart. Diagnostic tests for the disease are described, and the test results explained. There is also a comparison made between Lyme disease and conditions often mistaken for it, such as fibromyalgia and chronic fatigue syndrome. In addition, the text outlines what individuals can do to avoid getting Lyme disease, as well as what the community as a whole can do to reduce the number of Lyme-carrying ticks.