This paper presents a codification of theory-based approaches that are applicable to adult learning situations. It also lists some general guidelines that can be used when selecting a particular approach or theory as a basis for planning instruction. Adult education's emphasis on practicality and the relationship between theory and practice is discussed in the first section of the paper. Section 2 presents theory-based approaches to teaching and learning in terms of those developed for youth and applied or applicable to adults and those that were developed specifically for adults. Approaches that are examined include John Dewey's problem solving, Ralph Tyler's identification of objectives, Kurt Lewin's group dynamics and change theory, and behaviorism, cognitivism, and humanism. The last section presents some general guidelines for choosing an approach for teaching or planning instruction for adults. (Author/CSS)