The inspirational title of this book suggests that it was conceived in the after-glow of the millennium celebrations. Indeed, the editors have drawn on lectures given at the year 2000 American Psychopathological Association meeting of the same title. The book is dedicated to the life and work of Samuel B. Guze, who was presented with the Joseph Zubin award at the meeting: that was the last occasion on which many of his friends and colleagues saw him before his death.

One of the difficulties facing editors of conference proceedings is that they generally have less direct control over chapter topics and content than editors of other multi-author books such as textbooks. This often means that the final product resembles the ‘curate's egg’: it is good in parts. Fortunately, John Helzer & James Hudziak have avoided such problems and this egg is good throughout. They have produced a fine text that is both scholarly in content and exciting to read.

The contributions have been collected into four parts, the first entitled ‘Definitional tensions’. A masterly opening chapter by Robert Kendell sets the current scene. This is followed by an intriguing dialogue between Professors Regier, Narrow, Wake-field & Spitzer about the methodological and definitional issues raised by large-scale epidemiological studies in the USA. The second part, ‘Defining psychopathology’, explores how functional imaging could be used to define phenotypes of affective disorders. Part 3 considers how longitudinal studies can be informative, with examples drawn from studies on alcohol use and attention-deficit hyperactivity disorder. The final part, ‘Exploring alternatives’, brings together four authors who have interesting ideas about how genetic studies may inform the definition of phenotypes.

In 1970, Sam Guze & Eli Robins wrote a seminal and much-quoted paper on the indirect validation of phenotypes in psychiatry. They were also the first to apply an operational approach to defining psychopathology. Since then, there has been much effort but little real progress, and ideas about defining psychopathology have not really advanced. However, this book provides an optimistic view of the future. The technological advances in neuroimaging and genetics hold considerable promise for new ways of thinking about phenotypes. This publication provides a starting point for all who wish to take up the challenge of defining psychopathology in the 21st century.