Aim: Contemporary radiotherapy clinical trials typically require complex three-dimensional (3D) treatment planning.This produces large amounts of data relating technique and dose delivery for correlation with patient outcomes.Assessment of the quality of this information is required to ensure protocol compliance, to quantify the variation intreatments given to patients and to enhance the power of studies to determine correlates of patient outcomes.Materials and methods: A software system (‘SWAN’) was developed to facilitate the objective analysis, qualityassuranceand review of digital treatment planning data from multi-centre radiotherapy trials. The utility of this systemwas assessed on the basis of its functionality and our experience of its use in the context of multi-centre clinical trialsand trials-support activities.Results: The SWAN system has been shown to have the functionality required for use in several multi-centre trials,including automated review and archive processes. Approximately 800 treatment plans from over 30 participatinginstitutions have so far been assessed with the system for several treatment planning scenarios. To illustrate this weinclude a description of the use of the system for a large-recruitment prostate radiotherapy trial being undertaken inAustralasia, including examples of how the review process has changed clinical practice.Conclusion: The successful implementation of SWAN has been demonstrated in a number of clinical trials. The softwareprovides an opportunity for comprehensive review of treatment parameters that could impact on clinical outcomes andtrial results. Such quality-assurance (QA) has previously been difficult or impossible to achieve, particularly for a clinicaltrial involving large numbers of patients. Such reviews have highlighted inconsistencies in clinical practice that havesince been addressed through feedback from the review process. The process of data collection and review should beundertaken by dedicated, experienced and skilled staff in order to ensure efficiency.