BACKGROUND: Pulmonary arteriovenous malformations are abnormal direct connections between the pulmonary artery and pulmonary vein which result in a right-to-left shunt. They are associated with substantial morbidity and mortality mainly from the effects of paradoxical emboli. Potential complications include stroke, cerebral abscess, pulmonary haemorrhage and hypoxaemia. Embolisation therapy is a form of treatment based on the occlusion of the feeding arteries to a pulmonary arteriovenous malformation and can prevent many of these debilitating and life-threatening complications. OBJECTIVES: To determine the efficacy and safety of embolisation therapy in people with pulmonary arteriovenous malformations including a comparison with surgical resection and different embolisation devices. SEARCH STRATEGY: We searched the Cystic Fibrosis and Genetic Disorders Group's Trials Registers (last searched 07 September 2009). We also searched the following databases: the Australian New Zealand Clinical Trials Registry; ClinicalTrials.gov; International Standard Randomised Controlled Trial Number Register; International Clinical Trials Registry Platform Search Portal (last searched 22 November 2009). We checked cross-references and searched references from review articles. Finally, we contacted manufacturers and specialised centres for unpublished and ongoing trials. SELECTION CRITERIA: Trials in which individuals with pulmonary arteriovenous malformations were randomly allocated to embolisation therapy compared to no treatment, surgical resection or a different embolisation device. Studies identified for potential inclusion were independently assessed for eligibility by two authors, with excluded studies further checked by a third author. DATA COLLECTION AND ANALYSIS: No trials were identified. As this was the case, no analysis was performed. MAIN RESULTS: There were no randomised controlled trials identified. AUTHORS' CONCLUSIONS: Currently there are no randomised controlled trials to support or refute embolisation therapy for treatment of pulmonary arteriovenous malformations. However, randomised controlled trials are not always feasible on ethical grounds. Observational studies suggest that embolisation therapy reduces mortality and morbidity compared to no treatment in patients. A standardised approach to reporting with long-term follow up through registry studies can help to strengthen the evidence base for embolisation therapy in the absence of randomised controlled trials. Future viable randomised controlled trials may compare different embolisation devices against each other.