It has been 5 years since publication of the first edition of Dr. Attarian's Clinical Handbook of Insomnia which at the time was the first significant cl- ical textbook dedicated to insomnia, an often overlooked but important me- cal problem. The book was very well received. There has now been sufficient new information on the subject to warrant a second expanded edition of this very useful volume. Then, as now, the approach is to emphasize the frequent biological causes of insomnia rather than to attribute it primarily to underlying psychological and emotional factors. This new edition is an impressive major effort, having been expanded from 14 to 23 chapters including an extensive revision and updating of previous chapters with new references and the ad- tion of many new authors. An entirely new section of the book deals with insomnia in special populations including teenagers, pregnancy, menopause, and the geriatric population. Other new topics include insomnia as enco- tered in primary care practice, the role of circadian rhythms, the contribution of sleep related movement disorders to insomnia, insomnia in pain disorders, and the interesting entity of paradoxical insomnia, in which there is a large d- crepancy between the objective and subjective estimation of quantity of sleep. This collection within a single volume of practical information concerning a common but often neglected disorder remains a very useful addition to the armamentarium of the general or specialty physician who wishes to properly address insomnia in an informed and responsible manner.