This paper examines three teachers' implementation of a new communicative English language curriculum in Libyan secondary schools. The teachers were observed for two weeks teaching a unit of material from this curriculum and subsequently interviewed to examine the rationales for their classroom practices. The analysis highlighted considerable differences between the intentions of the curriculum and the instruction observed. In articulating the bases of their teaching, the teachers provided evidence of the ways in which their prior beliefs about language teaching and learning interacted with elements of their educational context to filter the planned curriculum. The manner in which they delivered the curriculum thus reflected their views of what was feasible in the light of their understandings of themselves as teachers, of their students, and of the demands of the system more generally, particularly in relation to assessment. Overall, this study provides evidence of the manner in which the uptake of an educational innovation can be limited when it is not congruent with and does not take into consideration the cognitive and contextual realities of teachers' work. This work thus has clear implications for the manner in which the link between intended reforms and teachers' actual practices can be strengthened. (Contains 1 table.)