With major advances in technology there are thousands of clinical and laboratory tests available. The first part of this handbook provides a patient-oriented approach to investigation where key symptoms and signs are described along with tests that may be of value in reaching a diagnosis. The remainder is speciality-centred and provides a comprehensive review of all available tests within a given subject. Contributors are all active clinicians who are engaged in medical practice, and who appreciate the problems faced by junior doctors. The handbook should also be of value to senior medical students, who will soon be on the wards and responsible for ordering tests on their patients.