This thesis addresses the research question of how social awareness support in computer systems for groups and communities can be designed in a successful way. While the field of human-computer interaction has been working with similar questions for more than 20 years, many aspects of people’s cooperation and the way those should be considered in system design still need further consideration and research. The thesis presents a number of projects where systems for cooperation have been designed for different settings and different kinds of use with a particular interest in social awareness. Drawing from the experiences of the different projects, design sensitivities around awareness, as a central prerequisite for collaboration, are suggested. Another contribution of the thesis is the presentation of a theoretical model for awareness, called Aether, introduced by us a number of years ago. We will discuss the theoretical implications of the model as well as a number of applications of it based on our own work as well as based on the work of other researchers who used Aether, by this providing confirmation of our model. Based on the findings around awareness, the thesis argues for a ‘translucent’ approach to the issue of socio-technical balance that one has to consider in the design process. Instead of trying to understand and model human behaviour or the social organization of cooperation, in order to ‘code’ them into the computer system, this approach advocates for systems that mediate information in a ‘translucent’ way so that people can retain the control of the organization of cooperation in their given context. By using a ‘reflective practitioner’ approach, the thesis discusses how people-centred methods have been used throughout these projects and looks into how awareness could be considered by using these methods. The focus of this investigation is twofold: on one hand to understand how the used methods have influenced our discussion about awareness and on the other hand it aims to address the practitioners of the field by questioning some of the common beliefs in the field. By investigating social awareness support in collaborative systems, the thesis contributes to theoretical arguments in the field of humancomputer interaction, and the area of CSCW in particular, while at the same time it provides the interaction design practitioner with a number of considerations for practical use. / QC 20100913