The first section of this paper reports the results of numerous literacy studies in which adults were tested on a variety of tasks, including filling out forms, answering questions about newspaper classified advertisements, and dealing with certain facets of consumer economics. The percentage of adults in the United States reported to be literate varied widely from study to study. In the second section, the author explores various definitions of literacy. Literacy has been defined as the ability to respond appropriately to all possible reading tasks, as the presence of reading skills necessary to enable persons to function effectively in society, and as the level of achievement attained by the average child by the beginning of fourth grade. Some researchers have attempted to define "functional literacy," which connotes reading for a purpose related in some way to social utility. The author concludes that literacy is related to specific tasks and specific contexts and that there can be no universal definition of literacy. In the United States, the minimum level of reading ability required for full participation in the social and economic life of the nation appears to be around the eleventh grade level. (GW)