Abstract The fast emergent and continuously evolving areas of the Semantic Web and Knowledge Management make the incorporation of ontology engineering tasks in knowledge-empowered organizations and in the World Wide Web more than necessary. In such environments, the development and evolution of ontologies must be seen as a dynamic process that has to be supported through the entire ontology life-cycle, resulting to living ontologies. The aim of this paper is to present the Human-Centered Ontology Engineering Methodology (HCOME) for the development and evaluation of living ontologies in the context of communities of knowledge workers. The methodology aims to empower knowledge workers to continuously manage their formal conceptualizations in their day-to-day activities and shape their information space by being actively involved in the ontology life-cycle. The paper also demonstrates the Human Centered ONtology Engineering Environment, HCONE, which can effectively support this methodology. Keywords: Semantic Web, Ontology Engineering, Human-Centered Computing, Knowledge Management 1. Introduction Ontologies are formal conceptualizations of domains, describing the meaning of (abstract and concrete) domain aspects by means of concepts and their interrelations (Chandrasekaran et al 1999). Ontologies have been realized as the key technology to shaping and exploiting information for the effective management of knowledge and for the evolution of the Semantic Web. Ontologies establish a common vocabulary for community members to interlink, combine, and communicate knowledge shaped through practice and interaction among community members, binding the knowledge processes of creating, importing, capturing, retrieving, and using knowledge (Staab et al 2001). The incorporation of ontology engineering tasks in knowledge-empowered organizations can prove to be a hindrance if not done in a way that is seamless to the day-to-day activities of the organization members (Vouros 2003). Traditionally, knowledge engineers develop the ontologies that are required by knowledge workers, and provide these ontologies for exploitation. However, due to constant updating, changing, and evolution of ontologies, there must be a close * Corresponding author: Tel: 0030 22730 82000, Fax: 0030 22730 82009, E-mail: kkot@aegean.gr Human-centered ontology engineering: The HCOME methodology Konstantinos Kotis * , George A. Vouros Department of Information and Communications Systems Engineering University of the Aegean Samos, Karlovassi, 83200 Greece {kkot, georgev}@aegean.gr