Background
Given the current financial constraints upon health services research and the failure of many trials to establish whether the lack of intervention effect is due to sub-optimal intervention design or implementation failure, it is increasingly important to consider pre-trial methods that a) provide leads on how the intervention works, and b) help maximise chances for the intervention to be effective. However, the decision-making processes of, and specific benefits associated with conducting pre-trial optimisation studies are still unclear. This multiple case study was conducted to gain researchers' experiences and views of the process of optimising complex health interventions.