Literacy acquired in childhood positively influences quality of life, but the effects of literacy acquired in adulthood are not well known. Experience shows that literacy is not easily disseminated to adults and that the skills of neoliterates are not stable. Dropouts, mastery, and retention rates are about 50 percent at each stage, so the effectiveness rate of some projects may only be 12 to 15 percent. As a result, literacy projects are now rarely funded by the World Bank despite requests from governments. To find causes for the low effectiveness of programs, two literature reviews were conducted on the topic of literacy in general and cognitive correlates of age and performance. It was concluded that: 1) adult illiterates seem to face a combination of social, motivational, instructional, and cognitive obstacles, which together prevent many from attending classes or mastering and retaining the material; 2) thus far there has been a tradeoff between quantity and quality in adult literacy - in previous decades, large-scale programs that taught literacy as an end in itself were less effective that smaller but more complex programs, which taught literacy as a means to carry out other activities; 3) apparently, no one ever becomes too old to learn sound-letter correspondences and to acquire basic literacy, but it is possible that functional literacy becomes increasingly difficult to acquire with age; 4) if it is indeed harder for adults to acquire functional literacy, perhaps large-scale literacy-only programs should target out-of-school children and adolescents (through the age of about nineteen years); and finally, 5) methodological improvements can increase the effectiveness ofliteracy programs.