The first three years of life present unique challenges to the study of psychopathology. We highlight four of the issues in a selective review of the developmental psychopathology of early childhood, including lack of specificity of risk and outcome variables, measurement difficulties, rapid developmental changes and the centrality of the relationship context in early childhood. We also highlight issues relevant to conceptualizations of disorders of infancy, emphasizing especially the need for efforts to validate clinical disorders. We consider two major domains of infant development that we believe are especially relevant to a discussion of psychopathology, namely, regulation of emotion and infant-caregiver attachment. Discussions of these two domains of infant development and their psychopathological extremes allow us to consider conceptualizations of psychopathology from the dual perspectives of developmental psychopathology and clinical disorders. We conclude by suggesting a number of strategies to build upon previous research.