The learning theories employed for the instructional design has shifted in its paradigm from behaviorism through traditional cognitive science to constructivist cognitive science. This paradigm shift demands for reconceptualizing learning and knowledge as well as the roles of the learner and teacher, instruction, subject matter, technology, and system. Among many variables which consist of the constructivistic learning environment, the concept of learning and knowledge seem to be the most fundamental, since these concept can alter the rest variables. As a work for reconceptualizing learning and knowledge, this paper first reviewed the concept of learning and knowledge in the views of behaviorism and cognitive theory. Each theory takes a different approach to objective specification, content analysis, leaner analysis, learning strategy, and learning assessment for instructional design. The constructivist congnitive theory advocates that the learning is a process of knowledge construction. 1n constructivistic learning envionmnt, learning is also knowledge-dependent, and highly tuned to the situation in which it takes place. Thus, the constructivistic learning should be occurred in learner-centered, knowledge constructed learning environment. Secondly, this paper attempted to investigate how constructivism might be interrelated with the other trends such as epistemological, psychological, philosophical, and methodological tradition. Epistemologically, constuctivism is contrasted to objectivism from which behaviorism can be drawn. As contrasted with objectivism, experientalism interprets that the thought is acquired and contstucted by the perception of experience, expecially expeience in physical and social environment. In this context, the constructivism corresponds to the experientalism when it recognize the reality in the world. In the tradition of philosophy, the constructivism is linked to pragmatism whereas the behavioristic theory can be linked to positivism. In addition, the pragmatic tradition meets with the qualitative research methodology. Therefore, the paradigm shift in instructional technology cannot be soly established and understood. Rather, it shares the ideas from the trends of epistemological, philosophycal, psychological, and methodological traditions in its inquiry. In order to accomplish this purpose, finally the knowledge base and knowledge structure was reviewed in three selected forms of knowledge: i) declarative verse procedural knowledge, ii) domain-specific verse strategic knowledge, and iii) structured verse ill- sutructured knowledge.