Since colonial times, definitions and estimates of illiteracy in the United States have been debated. The Census Bureau's major indicator is number of years of schooling completed. However, average grade-level attainment is high, whereas estimates of levels of reading ability remain low. In addition, these measures are inadequate for adults. A National Assessment of Educational Progress study concluded that although young adults could read and write, too many perform at low levels of proficiency. Increasingly complex definitions of literacy are accompanied by rising literacy standards, although some argue against a national standard definition, because literacy may have different connotations depending on the setting. Particularly in the workplace, the definition of literacy should be expanded beyond reading and writing to include a continuum of interrelated reasoning and communication skills. (Addresses and telephone numbers are provided for nine people who are sources for definitions of literacy. Three additional sources of information--the Division of Higher Education and Adult Learning, U.S. Department of Education; Library Programs of the U.S. Department of Education, and the Reading Reform Foundation--are listed.) (CML)