The existing knowledge base on child development offers a wealth of information that can be useful for the design of children's technology. Furthermore, academic journals and conference proceedings provide us with a constant stream of new research papers on child-computer interaction and interaction design for children. It will require some effort from designers to gather and digest the scattered research results and theoretical knowledge applicable to their products. We conducted an extended research project whereby the existing knowledge relating to the design of technology for children aged five to eight have been gathered and presented in a way that makes it accessible and useful to designers in practice. This paper provides and extract from that research, focusing on ten useful lessons learnt from existing literature. Categories and Subject Descriptors