Sonographic demonstration of an abnormal kidney as the presenting feature of tuberous sclerosis has not been described previously. A large echogenic kidney was first shown on routine prenatal 28 week ultrasound and confirmed as cystic on biopsy after birth. Generalized convulsions and depigmentation developed in infancy and CT showed cerebral cortical tubers. An enlarged echogenic left kidney was discovered on routine antenatal sonography of a 28 week fetus in a 27-year-old gravida 1 mother (see Figs 1 and 2). The previous 16 week ultrasound scan was normal. A provisional diagnosis of multicystic dysplastic kidney was made in view of the normal right kidney and bladder. A detailed fetal ultrasound at 32 weeks confirmed the unusual appearance of the left kidney, but did not detect any abnormality in the contralateral kidney, the head or the heart.