AimsWe describe how patient and public involvement (PPI) was integrated into the design of an intervention for a randomised controlled trial (RCT) based within primary care. The RCT, known as the PLEASANT trial, aimed to reduce unscheduled medical contacts in children with asthma associated with start of the new school year in September with a simple postal intervention, highlighting the importance of maintaining asthma medication for helping to prevent increased asthma exacerbations.BackgroundPPI is a key feature of UK health research policy, and is often a requirement of funding from the National Institute for Health Research. There are few detailed accounts of PPI in the design and conduct of clinical trials in the PPI literature for researchers to learn from.MethodsWe held PPI consultation events to determine whether the proposed intervention for the trial was acceptable to children with asthma and their parents, and to ascertain whether enhancements should be made. Two PPI consultation events were held with children with asthma and their parents, prior to the research commencing. Detailed field notes were taken by the research team at each consultation event.FindingsAt the first consultation event, parents and children endorsed the trial’s rationale, made suggestions to the wording of the trial intervention letter, and made recommendations about to whom the letter should be sent out. At the second consultation event, parents discussed the timing of the intervention, commented on the lay summary of the Research Ethics Application, and were invited to join the trial’s steering committee, while the children selected a logo for the study. PPI has resulted in enhancements to the PLEASANT study’s intervention. A further PPI consultation event is scheduled for the end of the trial, in order for children with asthma and their parents to contribute to the trial’s dissemination strategy.