The purpose of the research is to develop a Public Use Microdata Sample file (PUMS) support service. The principal benefit of this service will be to give scientists and demographers access to the PUMS data at their desktop computers. This service will provide microdata samples on CD-ROM for every census year for which they have been released. Currently the census sample data are available for nine census years between 1880 and 1990. IDD will create CD-ROM volumes containing each of these files. Each CD-ROM volume will contain data, tailored software, and users documentation. The software will be a microcomputer version of CENTS-AID, IDD's mainframe software for processing microdata files. CENTS-AID will be modified to change it from COBOL generator to a stand alone system, and to change its access method to one more suitable for the CD-ROM environment. IDD will continue to research begun in Phase I to determine the best way to increase the processing speed on CD-ROM. Both innovative data compression techniques and other file access methods will be explored. The PUMS support service will be implemented in this Phase II time period. Each CD-ROM disk is expected to be priced for less than $200, including user support.