Angiomyolipomas (AMLs) are renal tumors that occur both sporadically and in association with tuberous sclerosis (TSC). TSC is an autosomal dominant disorder characterized by hamartomatous lesions in multiple organs. Two TSC loci are recognized TSCl on 9q34 and TSC2 on 16pl3. Loss of heterozygosity (LOH) at the TSCI and TSC2 loci in lesions from TSC patients has recently been reported. Lesions that are not associated with TSC have not been previously examined for LOH at the TSC loci. We analyzed 29 renal angiomyolipomas from patients without a history of TSC. Three tumors demonstrated LOH on I6p 13. This is the first report indicating that mutations in TSC2 occur in tumors of patients who do not have TSC. We also found LOH on I6p 13 in 5 of 8 TSC‐associated AMLs. Two of these tumors were from a single patient and demonstrated different regions of LOH. These findings support the hypothesis that the TSC2 gene functions as a tumor suppressor.