A five-year program of research in adult learning is reported upon. One purpose of this program was to determine age differences in cognitive abilities, with special reference to items selected as suitable for adults of different ages, to survey the educational backgrounds and skills that older and younger adults bring to learning situations, and to study age differences in personality characteristics of a type likely to influence the individual's learning. A second main purpose of the research was to investigate experimentally the interaction of the variables mentioned above with the age of the learner in determining learning and performance. The general plans and results for these two aspects of the program of research are described in Parts I and II of the report. Part I, Adult Age Differences in Cognitive Abilities, Educational Background, and Learning Orientation, discusses adult age differences in cognitive functioning, in educational background, and in learning orientation. Part II, Experimental Studies, discusses effects of performance; and age, stress, and cognitive performance. Four appendixes present Tests Developed & Means and Standard Deviations for Each Age Decade, Sex and Education on Test scores, educational and occupational level; Responses by Age Decade on test items; and Paired Associate Word Lists. (DB)