A synchronous study has been performed on four years of the International Conference on Information systems (ICIS) proceedings, to determine the obsolescence rate for the field of information systems (as reflected in the sub-topics covered by the ICIS conference). IS is found to have a relatively high obsolescence rate, similar to that of fields in engineering and the technology-dependent "hard" sciences. In addition, this study provides a categorization of the types of documents referenced by IS research, and presents an analysis of the obsolescence rate for these types. This type of categorization permits a finer-grained examination of patterns of information dissemination and use.