Examined developmental theory and its relevance for the practice of clinical child psychology. Following a brief review of basic principles of developmental psychology and developmental psychopathology, implications of a developmental perspective are explored for the diagnosis, assessment, and treatment of childhood disorders. Although it is obvious that many developmental issues confront the clinical child psychologist and that we have learned much about translating developmental theory into clinical practice, we conclude we have a long way to go before we can assert that a true developmental-clinical child interface has been realized.