This master’s thesis investigates the design and evaluation of a social awareness system. We do this by conducting two different activities. First we design a social awareness system, which involves several sub-activities: We survey a selection of previous study papers to discover how social awareness systems have previously been designed. We identify three characteristics that influence design: characteristics of technology, the context of social technologies and social relations between users. Based on our model of mediated social awareness and the survey we design a system, iSocialize, to exemplify social awareness. Our second activity, which is designing an evaluation method, is also constructed from several sub-activities: again we survey a selection of previous study papers, but this time to discover how social awareness systems have been evaluated. We identify the following two distinctions: the system’s level of functionality and the purpose of the evaluation. From this survey we construct an evaluation method that focus on the social relations of evaluation participants. We construct an evaluation method and conduct 10 tests with pairs of acquainted participants or unacquainted participants. iSocialize serve as the case for this evaluation. We end the process by reporting the results of evaluating the concept of social awareness and on the applicability of our evaluation method for social awareness methods. The conclusion of this master’s thesis is that we successfully implement the properties activity, status, vicinity and relation into iSocialize, and that acquainted as well as unacquainted users can be used for testing social awareness systems, but for different purposes.