 1. The normalization process theory, NPT, addresses the factors needed for successful implementation and integration of interventions into routine work. 2. NPT can act as a sensitizing tool, enabling researchers to think through issues of implementation while designing a complex intervention and its evaluation. 3. Trialists can use NPT to improve trial design by highlighting potential problems with recruitment or data collection, as well as ensuring the intervention has good implementation potential. This article was authored by Yong Bee, O'Donnell Catherine, Mayor Francis, and others.