Comprehensive evaluation is often ignored in much of the development of computer-facilitated learning materials. We need to understand what learning difficulties students have, offer them experiences which allow them w construct coherent and useful mental constructs, and then find out whether we are successful. Formative evaluation involves considering how students perceive elements such as navigation, visual material, formats used for questions, etc. This process of information interchange between developers/teachers and students can provide valuable insights into how students approach learning. Summative evaluation focuses more on whether students can demonstrate attainment of certain learning objectives. Both formative and summative evaluations are needed. In this paper qualitative methods of evaluation will be emphasized. Some evaluation questions are posed in the paper and suitable evaluation strategies which can assist in answering these questions are suggested, such as expert reviews, usability testing, instructional modelling, observations, individual and group interviews, questionnaires, performance measures, and computer logging of student work. Evaluation data from three innovative science projects will be described in the paper.