There are gaps in global understanding about how to design and implement interventions to improve sanitation. This formative research study provided insights for the subsequent redesign of a government-led national sanitation campaign targeting rural populations in Tanzania. The Behaviour Centred Design approach was used to investigate the determinants of toilet building, improvement and use. Varied, novel, and interactive research tools were employed in fifty-five households in two regions of rural Tanzania. Results were analysed to articulate a Theory of Change, which then informed intervention design
