Twenty-three patients (6 men and 17 women) with renal angiomyolipoma (AML) were analyzed. They were divided into two groups; 9 patients in the operated group and 14 patients in the surveillance group. The operations for AML were performed on 3 patients suspected of having renal cancer or 6 patients with an AML more than 5 cm in size who had some symptoms as a result of the presence of the tumor. The patients in the surveillance group had tumor less than 4 cm in diameter, and did not have any symptoms. No changes in tumor size were observed during the intervals between observation checkups. The male to female ratio, the average age and the location of AML were not significant in either group. However, the tumor size was significantly larger in the operated group. Thus, the tumor size is considered to be an important factor when deciding the necessity of surgical treatments for AML. Pre-operative diagnosis and treatment strategies, including thin-section computed tomography and selective arterial embolization for AML were discussed.