This is the fourth in a series of reports that draws upon the vast amount of background and assessment data and information that have been collected from the National Adult Literacy Survey (NALS) and the International Adult Literacy Survey (IALS). In this report, the authors find connections between the literacy skills of adults and their success in the labor market during the 1990s. In addition to describing the population's prose, document, and quantitative proficiencies, the authors report on the relationship of these adults' skills to their socioeconomic characteristics, labor force activity and experience, weekly wages and annual earnings, and their recent education and training activities. The authors also compare the literacy of the U.S. labor force with the literacy of workers in other countries, and they examine the influence of that proficiency on an array of labor market outcomes and behaviors. The analyses reveal large differences in the literacy skills of U.S. workers in various occupations and demographic groups. They attribute important differences in earnings and other labor market outcomes and behaviors to these literacy gaps. The data show that workers with higher levels of literacy were more likely to participate in education and training, which the authors believe contributes to the growing gap between the "haves" and "have-nots." Particularly disturbing is the finding that many workers with limited literacy skills are not aware of that limitation, decreasing the likelihood that they will seek help. Suggestions are offered for addressing the problem and are a reminder that strengthening the literacy skills of U.S. workers is necessary for achieving equality among groups and for realizing the nation's potential for economic growth. The following are appended: (1) Unemployment Rates and Employment/Population Ratios of U.S. Adults (Age 16 and Older) by Literacy Proficiency Level; and (2) The Mean Literacy Proficiencies of U.S. Adults by Labor Force Status.