Population censuses became universal in the last half of the twentieth century. Will census microdata samples become universal in the first half of the twenty-first? From 1985 through 1994, of 153 countries with populations of one million or more, 134 conducted enumerations in the 1990 round of censuses. 94% of the world's population was counted (Table 1). 54 countries provided researchers access to anonymized census samples of individuals and households. Some countries restricted access to a single investigator or research facility, but what is remarkable about the 1990s is not only the globalization of the census, but the growing acceptance of anonymized samples as statistical instruments. Once requirements of statistical confidentiality are assured, such samples are suitable for distribution to researchers. The availability of census microdata samples for more than 50 countries is now driving an effort to harmonize census microdata chronologically and spatially. The IPUMS international project proposes to harmonize census concepts and codes at the microdata level for both contemporary and historical census samples and disseminate the integrated database to bona fide researchers via the Internet.