The expression psychopathology in general and child psychopathology in particular, is affected by multiple sources of variance. Some of these sources include gender differences, informant differences, and age-related differences. In this paper, we discuss how these sources of variance complicate both research and clinical management. We argue that the current diagnostic system would be aided by the inclusion of a quantitative axis that can take these sources of variance into account. We reason that the fields of genomics and neuroscience are prepared to move the field of developmental psychopathology forward, but need a diagnostic system that allows for these sources of variance to be controlled. We demonstrate how in Conduct Disorder, inclusion of dimensional information would allow the clinician or researcher to demonstrate not only the presence or absence of pathology, but also the degree to which the disorder is manifested in a particular individual. Because dimensional approaches are already used widely as an alternative measure of psychopathology, we argue that there is reason to consider dimensionalizing some aspects of the DSM. Copyright © 2007 John Wiley & Sons, Ltd.