This study examined changes in student motivation and achievement in science during a visit to a university children's science museum. The study was based on the pretest-posttest control comparison group design with four treatment groups: control, exhibit, lesson and exhibit/lesson. The sample consisted of 228 sixth-grade students from a Louisiana public school who were randomly assigned to one of the four experimental groups. Pretest, posttest and delayed posttest measures of intrinsic motivation and achievement in science were obtained using the Children's Academic Intrinsic Motivation Inventory and an achievement test written to measure areas of science incorporated in the museum exhibits. The data were analysed using a one-way ANOVA, dependent "t" tests and Pearson "r." Significant differences were found within groups for (1) the lesson group in motivation and (2) the exhibit group in achievement from pretest to posttest and from posttest to delayed posttest. A significant relationship between level of motivation and science achievement was revealed for the exhibit group on the delayed posttest. There were no other significant findings to support that the treatment led to any long-term effects on motivation or achievement within any of the four experimental groups.