Research into learning in informal settings such as museums has been in a formative state during the past decade, and much of that research has been descriptive and lacking a theory base. In this article, it is proposed that the human constructivist view of learning can guide research and assist the interpretation of research data because it recognizes an individual's prior knowledge and active involvement in knowledge construction during a museum visit. This proposal is supported by reference to the findings of a previously reported interpretive case study, which included concept mapping and semistructured interviews, of the knowledge transformations of three Year 7 students who had participated in a class visit to a science museum and associated postvisit activities. The findings from that study are shown in this report to be consistent with the human constructivist view of learning in that for all three students, learning was found to be at times incremental and at other times to involve substantial restructuring of knowledge. Thus, we regard that the human constructivist view of learning has much merit and utility for researchers investigating the development of knowledge and understanding emergent from experiences in informal settings. The theoretical and practical implications of these findings for teachers and staff of museums and similar institutions are also discussed. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 177–199, 2003