This is the updated and revised manual for the MacArthur-Bates Communicative Development Inventories (CDIs), which are standardized, parent-completed forms for assessing language and communication skills in infants and young children. This new edition provides more detailed instructions for administering and scoring the forms; an expanded set of normative data and guidelines for using this data; an overview of the CDI-III, which is for use with slightly older children; information on new scanning and automated scoring options; updates on research and clinical findings, plus expanded reliability and validity reports; and background information on the development of the forms.