Over the past few years, curriculum innovation has been regarded as an essential strategy for educational reform throughout the era of educational change. Because of the changing nature of the knowledge age, students need to develop ways of dealing with complex issues and problems that require different kinds of skills and knowledge they have ever learned. Given the advancement of information and communications technologies (ICT), a number of cases of building learning communities in classrooms have been developed in recent years. Realizing the impact of this new learning culture, six primary schools in Hong Kong participated in the implementation of building learning communities through science project works. During the project, students from different schools engaged in the discussion and knowledge construction using a computer mediated communication (CMC) platform called Knowledge Forum. The aim of this case study is to explore the role of ICT in building learning communities and the conditions are essential to building learning communities from the different ways that students and teachers experienced the processes of community and knowledge construction using Knowledge Forum. Through the analysis of the interviews of students and teachers, conditions that support learning community building were emerged in three major themes, namely; conceptions of learning, knowledge construction processes, and development of social processes. [Copyright of Educational Media International is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/0952398032000092198]