Tuberous sclerosis complex (TSC) is more prevalent than previously believed and most cases result from new mutations and, hence, do not have affected relatives. Many patients who meet the new diagnostic criteria have unrecognized skin lesions and/or occult lesions in internal organs. As early diagnosis and appropriate intervention can reduce morbidity and mortality from the neurologic. renal, and pulmonary complications of TSC, physicians should be alert for the dermatological signs of the condition and for the incidental finding of TSC lesions during diagnostic testing. Patients with TSC may be asymptomatic and of normal intelligence. We report a case of TSC diagnosed by the incidental finding of renal lesions in a young woman during pregnancy ultrasonic examination.