OBJECTIVE The purpose of this study was to retrospectively evaluate tumor necrosis following preventive embolization in patients with renal angiomyolipoma (RAML) at high risk of bleeding. METHODS Arterial embolization was performed in 24 patients (22 women, 2 men; mean age, 43±13 years) with a total of 30 RAMLs (mean volume, 137 cm(3)±163) between 1996 and 2012. Two sub-groups of patients were identified and further compared based on the presence or not of necrosis following arterial embolization. RESULTS The technical and clinical success rates of arterial embolization of RAMLs were 97% and 87%, respectively. The mean initial volume of RAMLs differed between the two sub-groups with 331 cm(3) in the group with tumor necrosis and 88 cm(3) in the group without tumor necrosis (P=0.0047). High-fat content RAMLs were predominantly observed in the necrosis group and the mean volume reduction observed for high-fat RAMLs was 65% whereas it was 36% for low-fat content RAMLs. The six patients who developed RAML necrosis had arterial embolization using microspheres (one patient with microspheres alone and five with a combination of microspheres and metallic coils). All necrotic RAMLs displayed arterial dysplasia. CONCLUSIONS The risk of tumor necrosis is higher for larger RAMLs. The role of distal arterial embolization with microspheres in tumor necrosis in RAML is suggested by the results of our study but could not be definitely demonstrated statistically due to the limited sample size.