Consistent with preceding volumes in this series, the contributors represent a variety of disciplines related to the theme of the conference and the ensuing volume. In the present instance, the theme is biological and neuropsychological mechanisms in life-span psychological development and the disciplines represented are behavioral medicine, neurology, neuropsychology, psychophysiology, and psychology. The theme is expressed in theories and findings about genetic and environmental mechanisms; brain mechanisms; relations of physiological functioning in infancy to later development; physiological risk factors in infancy, adolescence, and old age; methodological and data analytic problems; and issues about the validity of neuropsychological assessment. This volume begins with overviews of theoretical and methodological issues and continues with chapters dealing with selected portions of the life span.