There are few published reports of adults with Williams syndrome (WS). We have evaluated ten adult WS patients. The patients in our study were very variable in clinical presentation, ranging from severely affected patients with complicated medical histories to mildly affected patients who are generally in good health. Cardiovascular anomalies and hypertension were frequent. Supravalvular aortic stenosis was seen in four patients, mitral valve prolapse in three, bicuspid aortic valve in one, valvular aortic stenosis in one, and pulmonary stenosis with right ventricular hypertrophy in one. Typical facial features included stellate irides, prominent cheeks, full lips, and micrognathia. Mental retardation was seen in all patients. Verbal skills were better developed than motor skills. All patients in our study lead active lives, and most are involved in sports. Some hold supervised jobs. Eight of our patients live with their parents and two in group homes. Independent living is restricted by their mental and adaptive limitations.