The Comparative Database System (CDS) provides a means for coding and using data on U.S. and international postsecondary educational activity and behavior. CDS permits education-data users to obtain accurate and reliable comparative data on postsecondary education questions. This document contains a discussion of the development of CDS, a detailed technical description of CDS and its relation to other databases, and advice about its use. CDS was developed as a systematic means for reporting and analyzing data provided by respondents to the Survey of Earned Doctorates (SED), but it can be used whenever comparative and international institutional or individual data need to be organized and analyzed. Section 1 is the overview and description background and development; concepts, definitions, and methodology; and implementation), while Section 2 (half the document) contains the data codes used in CDS (geographical regions, countries, country subdivisions, primary language of instructor, standard program types, institutional types, and standard program completion awards and institutional levels (Contains 245 references.) (SLD)