Angiomyolipomas were found in 42 kidneys in 23 female and 8 male patients at our medical center. Angiomyolipoma was diagnosed by computerized tomography (CT) alone in 55% of the cases, and by a combination of ultrasound and CT in 36%. Nine of 11 patients with bilateral angiomyolipoma had associated tuberous sclerosis. Treatment consisted of observation in 22 patients, selective arterial embolization in 6, partial nephrectomy in 6 and nephrectomy in 8. A total of 17 patients who were observed had tumors smaller than 4 cm. and 4 h had angiomyolipoma of 4 to 10 cm. With a mean followup of 3.8 years, no observation patient had subsequent renal hemorrhage and only 1 (tumor larger than 10 cm.) had radiographic progression. Despite progression, the latter patient remained asymptomatic for 18 years. Selective arterial embolization (3 tumors 4 to 10 cm. and 3 larger than 10 cm.) resulted in preservation of renal function at a mean of 1 year. All patients treated with partial nephrectomy (6 tumors 4 to 10 cm.) maintained stable renal function without recurrence during a mean 4.7-year followup. Similarly, all individuals who underwent nephrectomy (4 tumors smaller than 4 cm., 3 tumors 4 to 10 cm. and 1 tumor larger than 10 cm.) have stable renal function. We recommend renal conservation for patients with renal angiomyolipoma using a strategy of observation for small asymptomatic tumors, partial nephrectomy for moderate size tumors and selective arterial embolization of large tumors not amenable to partial nephrectomy.