The preoperative diagnosis of renal angiomyolipoma should be made in virtually every case because of characteristic clinical and radiologic findings. The clinical, sonographic, computed tomographic, and angiographic findings in 28 patients with this lesion are reviewed. The sonographic findings of increased echogenicity in a renal mass can be helpful in suggesting the diagnosis of renal angiomyolipoma, and the detection of fat in the renal tumor by CT is diagnostic. It is important to make a preoperative diagnosis of this lesion so that the correct treatment approach will be instituted.