This study examined how a professional development program which incorporates the use of electronic data-loggers could impact on science teachers' attitudes towards inquiry-based teaching. The participants were 28 science or technology teachers who attended workshops offered in the United States and Japan. The professional development program emphasized (a) guided inquiry activities, (b) participants' own exploration within the range of given tasks, (c) instructors' guidance on the processes of inquiry and technology, and (d) discussions of the ways to bring their inquiry experiences in their classrooms. Data sources included field notes, video recordings, artifacts, and survey responses. Analysis of participants' discourse identified many instances in which the program helped the teachers deepen their understanding of inquiry-based teaching. The findings are presented as three assertions: (a) all the elements incorporated in the program contributed positively to participants' engagement in inquiry, (b) connections between participants' sensory experiences and graphical representations of data led them to have new understanding of the phenomena under the investigation, and (c) there were strong connections between their experiences about inquiry and teaching strategies that they wanted to incorporate in their classrooms. Applications of the findings into the development of more effective professional development programs will be discussed. (Contains 2 tables and 3 figures.)