A longitudinal case study focused on the process of conceptual change in science of a young girl. The subject, the researcher's granddaughter, was 6 years and 6 months old and in first grade when the first of 19 hour-long sessions began. Sessions were spread over a two-year period. A concurrent case study was being conducted with the researcher's grandson. Tradebooks and discussion were used to provide scaffolded and developmentally appropriate science instruction. Data included field notes and interviews. Results indicated that (1) the developmentally appropriate instruction enabled both children to restructure their alternative conceptions of scientific principles; (2) both seemed to follow the same process of conceptual change (they at first held onto their ideas despite instruction, then underwent a period when they held alternative conceptions and ideas consistent with scientific understanding at the same time, and finally a time when they abandoned their alternative conceptions); (3) both children had to be encouraged to have confidence in themselves as learners at the same time that their confidence in their original ideas was being challenged for conceptual change to take place; (4) neither child demonstrated any evidence of a misconception about the cause of the seasons; and (5) the girl's response to anomalous data was to reject it while the boy appeared to accept it but did not retain it. Findings suggest that it is important to encourage young girls to show an interest in science and have confidence in their ability to learn and do science.(Contains 32 references and seven figures.) (RS)