The paper reports on the outcomes of a study that utilized a graphical tool, Digalo, to stimulate argumentative interactions in both school and informal learning settings. Digalo was developed in a European study to explore argumentation in a range of learning environments. The focus here is on the potential for using Digalo in promoting argumentative interactions of students in primary science, first, in a school-based context of students investigating and learning about electricity, and second, in a hands-on science discovery centre where students are interacting with different scientific phenomena. Data sources included observations of students using Digalo in the two contexts and the resultant Digalo maps. Analysis of observations focused on students' engagement and interactions, and of Digalo maps in terms of the process and content of argumentation. A previously developed level system was used to evaluate the process of argumentation. The study has revealed some limitations of Digalo as a teaching resource, but has provided insights into ways in which students build their knowledge with the help of Digalo as they interact with each other and with scientific phenomena. (Contains 1 table and 3 figures.)