High morbidity has been reported for free vascularised reconstruction for osteoradionecrosis (ORN) and there are no apparent risk factors. A single nucleotide polymorphism in the transforming growth factor beta 1 gene (TGF-β1) has been implicated in the cause of ORN and may also predict these complications. We studied a series of 30 consecutive patients who had had reconstruction for severe ORN with free tissue transfer in relation to their outcomes and complications for a number of risk factors including TFG-β1 genotype, age, sex, comorbidities, site and stage of tumour, type of initial operation, and dose of radiotherapy or chemoradiotherapy. Two patients died and 2 flaps failed. Using the Clavien-Dindo classification, 16 patients developed grade III complications and 6 grade II. Median (IQR) duration of inpatient stay was 19.5 (12-25) days and the median (IQR) duration of outpatient treatment was 6 (4-11) weeks. No specific risk factors for postoperative complications were identified. In view of the severity and unpredictability of the complications, careful preoperative counselling of patients is essential.