This paper describes a study into the implementation within two Spanish primary schools of an inquiry-based curricular project entitled "Exploring Our World" (ages 6-12). Taking the form of two case studies, it offers a description of the two participating schools and the development of the project within them. Particular attention is given to the conceptions, difficulties, obstacles and facilitative factors which influenced the teachers' attempts to introduce inquiry-oriented practices into their classrooms. The study has a markedly qualitative focus and aims to provide an insight into the experiences of those involved, with a view to informing other groups interested in following this approach. Among the conclusions that can be drawn from the project, most notable are the influence of the level of professional development on the introduction of inquiry-based approaches and the absence of a single model of implementation; each initiative is necessarily subject to its particular configuration of context and stakeholders. Nevertheless, all those participating in this initiative were in agreement that involvement in projects of this type is favourable to teacher development and the quality of teaching. (Contains 1 table and 1 note.)