This dissertation, "The Effects of Social Capital on Construction Project Success: Exploring the Mediating Role of Project Learning" by Tas Yong, Koh, 許達雄, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Construction project organisation is a complex human system. Despite the formal governance structure of project, construction works and activities still rely primarily on informal personal contacts of the participants. It is the "here-andnow" interactions and mutual adjustment of project participants that underpins daily construction operations. From the perspective of social learning theory, human interactions in project organization involve learning. In this context, the social nature of learning comes to prominence. Learning embodies the accommodation and adjustment of the project participants' expectation and tacit nuances prevalent in the interactions among participants. As a human system, the organization of project participants in a project forms a social network. The relational links of participants embedded within the network act as an important resource. This resource, especially the goodwill engendered among the participants, can be used to facilitate actions. Such goodwill is referred to as social capital. The combination of these two perspectives enables the construction of a model of the project team. Social capital engendered in the project organization can be appropriated to facilitate positive actions. In this line of conception, the network of relationships among the project participants may offer mutual support for the cultivation of reflective practices and learning in terms of adaptation, integration, and cooperation. Because social capital is the primordial form of social phenomenon, it is postulated that social capital provides the conditions necessary for learning to take place, and learning, in turn, contributes to project success - that is, project learning mediates the impact of social capital on project success. To test this hypothesis and a series of other related propositions, empirical studies had been carried out within the Hong Kong construction industry. Both quantitative and qualitative approaches were adopted in the empirical studies - questionnaire survey and case studies were conducted. Findings reveal that a more integrative procurement arrangement, management commitment, project team appraisal system that emphasises team working, participants' intensive interactions, positive personality all contribute to the formation of project social capital, while multiple managerial hierarchies, subcontractor-induced problems, government transparency requirement, goals mismatch, and bureaucratic contract administration all impede its formation. In project organisation, the overlapping of both formal and informal organisational structures occupied by personnel with both technical and managerial capabilities improves project organising efficiency. Indeed, with the mediational thesis generally supported - the impact of social capital on project performance is mediated through learning - and the emergence of a new personal dimension, social capital is a critical antecedent to project organising. However, because social capital and learning affect the soft rather than hard success criteria, other factors need to be considered for overall project performance. These other factors are the capabilities of all project parties and the adoption of relational contracting norms and behaviours. It is the combination of all these factors with social capital as the substrate of part