The purpose of this book is to give the basic neuroscientist and the psychiatrist an overview of psychopharmacology,that relatively recent branch of pharmacology which is concerned with the study of drugs used to treat mental illness. The scope of the subject also covers the use of drugs and other chemical agents as tools that enable the researcher to investigate how the brain functions. This is one of the most rapidly advancing fields of medicine and therefore any short textbook on the subject is bound to omit many aspects of the subject which are fundamentally important. Nevertheless, based on several years of experience teaching psychopharmacology to undergraduates and to postgraduate clinicians studying for their membership examination for the Royal College of Psychiatrists, the author has tried to emphasize the practical advantages of understanding how psychotropic drugs work, not only because this may lead to an improvement in their therapeutic use but also that their side effects may be predicted. A brief glance through this book will persuade the reader that this is not a cook book containing proprietary drugs names, doses and a list of side effects. Neither has the author attempted to give anything but a brief synopsis of the clinical features of the psychiatric illnesses for which the psychotropic drugs are used. There are many good texts available that cover clinical aspects of psychiatry and most countries have produced excellent formularies to provide practising clinicians with a summary fo the therapeutic uses and side effects of psychotropic drugs in common use. It is hoped that the reader will not only gain some insight into psychopharmacology as a result of this text but, more importantly, of its value in enabling the basic and clinical neuroscientist understand how the brain works in health and disease.