Current definitions of illiteracy and functional illiteracy are reviewed, and their relationship both to estimates of the scope of the problem and to efforts toward its solution are discussed. Applying functional standards according to the requisites of particular societies, it can be seen that even countries with high literacy rates, such as the United States, harbor large functionally illiterate populations. It is argued that adult basic education efforts in the United States and abroad should be planned on a situation-specific basis, with goals, content, and evaluative components derived independently of the usual grade school equivalencies. (Editor/CK)