The paper discusses about the need for an ontological approach for a clinical decision support system (CDSS) in an acute postoperative pain management (APPM) setting.The paper describes the current issues in APPM,namely prescribing and technical errors due to clinicians' negligence of local guidelines,lack of continous education and confusion on responsibilities and roles.The paper reviews about structured approaches to improve APPM which is to develop guidelines and algorithms,clinical paths,checklists,daily goals and improvement to health information systems.The approaches can be utilized by using an ontological approach to computerize the key concepts and relationships in APPM to allow terminology management,integration,interoperability and sharing of data,knowledge reuse and decision support.Few deatures that are important for CDSS are highlighted in this paper. A number of previous studies on the use of ontology to solve biomedical problems are also discussed. The paper also proposed the methodology for designing and developing an ontology-based CDSS for APPM. Keywords: Ontology, clinical decision support system, acute postoperative pain management.