With reference to the literature on adult self-directed learning, a model termed the "Two-Shell Model of Motivated Self-Directed Learning" was formulated that differentiates sociohistorical environmental conditions, internal conditions, and activities related to four concepts (interest, learning strategies, control, and evaluation). The following hypothesis guided the study: interest in self-directed learning, selection of learning strategies, control of the application of those strategies, and evaluation of the results of self-directed learning are related to individual experience of autonomy, competence, and social integration. The hypothesis was tested through a survey of 194 employees of a German medical insurance company and 67 employees in the fish processing industry. It was concluded after an analysis of the responses that self-directed learning may be viewed as a dynamic interplay between interests, motivations, strategies, control, and evaluation and that self-directed learning is related to environmental conditions experienced. It was stated that self-directed learning must be differentiated and that self-directed learning is heavily influenced by perceived environmental conditions. It was recommended that companies adopt made-to-measure personnel and organizational development policies and practices in the 21st century. (Contains 28 references) (MN)