Noonan syndrome affects approximately 1 in 1500 live births. Affected individuals may have characteristic phenotypic features some of which are shared with Turner syndrome, although in Noonan syndrome the karyotype is normal, unlike the 45X karyotype of Turner syndrome. Renal anomalies have been described in both syndromes and in Turner syndrome they are both common and frequently severe. The frequency and spectrum of renal anomalies in Noonan syndrome have not been well documented. Upper abdominal ultrasound was performed to establish the frequency of renal anomalies in Noonan syndrome. Forty-four individuals with Noonan syndrome, aged between 9 months and 38 years, were studied. Sixteen scans (36%) were normal and 28 (64%) were abnormal. Five patients (11%) had renal anomalies. Twenty-three patients (53%) had splenomegaly, 6 of these with associated hepatomegaly. One patient had a choledochal cyst and a midgut malrotation. The frequency of renal anomalies in Noonan syndrome is 11%, which is lower than that seen in Turner syndrome. However, splenomegaly with or without hepatomegaly occurs commonly. Choledochal cyst and solitary kidney, previously unreported in Noonan syndrome, are documented.