Case-based reasoning (CBR) is a methodology in Artificial Intelligence (AI). A case is a situation, episode, etc. remembered (stored) by a computer, and the attempt to reuse it is the subject of case-based reasoning [3,4,5]. CBR reasons by means of past cases stored in its case library, by retrieving similar cases in the past matched against the user input problem situation, and then using pre-defined adaptation knowledge to reuse the retrieved case to fit current situation. This paper presents the basic concepts of CBR, its reasoning cycle, the major classes of adaptation methods used in CBR and a brief introduction of case-based adaptation (CBA). In addition, several applications of CBR in Macau are presented in the paper.