The unique characteristics of tablet PCs promise important benefits for education. Yet, little is known about the rationale underlying teachers' decisions concerning their educational uses within the constraints of daily classroom practice. The current multiple case study investigated the practical considerations informing nine secondary school teachers' decision-making processes regarding the use of tablet PCs. Stimulated recall interviews revealed 10 criteria underpinning teachers' instructional decisions. Four criteria influenced the degree of congruence with teachers' previous practices: familiarity, alignment with course content, opportunities to achieve (new) instructional goals efficiently, and compatibility with established pedagogical beliefs. Costs and benefits of tablet PCs were determined in terms of educational added value, lesson preparation requirements and potential disruptions to the learning environment. Finally, access to a solid technology infrastructure, supportive school policies and knowledge of how to effectively integrate tablet PCs with course content were identified as important pre-conditions for sustainable implementation. Overall, the results suggest that practical concerns constitute a critical element in teachers' decision making, influencing not only teachers' intention to adopt tablet PCs, but also the ways in which they use this technology to support instruction.