Ubiquitous applications are embedded in intelligent environments integrated into the physical world and composed of users with different preferences, heterogeneous devices and several content and service providers. Moreover, they focus on offering services and contents anywhere and at any time by assisting the users in their daily activities without disturbing them. Based on this idealized world, the anywhere and at any time paradigm poses some challenges for the Software Engineering community, such as: device heterogeneity, distributed environments, mobility, user satisfaction, content adaptability, context awareness, privacy, personalization, transparency, invisibility and constant evolution of technological trends. In order to deal with these new technological challenges, we propose a Reuse-Oriented Approach for Incremental and Systematic Development of Intentional Ubiquitous Applications. We have chosen two main goals that drive our research in this thesis: (i) the construction of reuse-oriented support sets based on an extensive investigation of ubiquitous applications and the Intentional-Multi-Agent Systems paradigm – i.e. Development for Reuse; and (ii) the incremental and systematic development of Intentional-Multi-Agent-Systems-driven ubiquitous applications based on the reuse-oriented approach – i.e. Development with Reuse. Some contributions of our work are: (i) a reuse-oriented architecture centered on support sets – i.e. building blocks mainly composed of conceptual models, frameworks, patterns and libraries – obtained from the Domain Engineering of Ubiquitous Applications; (ii) a reuse-oriented Ubiquitous Application Engineering for incremental and systematic development of intentional ubiquitous applications centered on the proposed building blocks; (iii) a reasoning engine focused on fuzzy conditional rules and the Belief-Desire-Intention model to improve the agents cognitive capacity; (iv) a specific mechanism based on intentional agents to deal with privacy issues by balancing privacy and personalization as well as transparency and invisibility; (v) a catalogue that graphically presents the main ubiquitous non-functionalrequirements, their interdependencies and ways to operationalize them based on the combination of traditional and emergent technologies; (vi) ontologies to allow the dynamic construction of interfaces and to improve the communication and inter-operability of software agents; and (vii) a dynamic database model to store and retrieve the ubiquitous profiles (e.g. user, device, network and contract profiles) by improving the data management on the fly. The proposed approach was evaluated by developing different ubiquitous applications (e.g. e-commerce and dental clinic ubiquitous applications).