Background: Evidence from the US Truth campaign suggests that interventions focusing on tobacco industry tactics can be effective in preventing smoking uptake by children. Operation Smoke Storm is the first school-based intervention based on this premise and comprises three classroom sessions in which students act as secret agents uncovering tobacco industry tactics through videos, quizzes, discussions, and presentations. We report a qualitative evaluation of its acceptability. Methods: We conducted eight focus groups with 79 students aged 11-12 who participated in Operation Smoke Storm at two UK schools in Autumn 2013, and 20 interviews with teachers who delivered the intervention. These were digitally audio-recorded, transcribed verbatim...