Williams syndrome (WS) is a well-recognized neurodevelopmental disorder manifested by both connective tissue and CNS abnormalities. The study depicts the 8-y experience and follow-up of 50 Greek children with the clinical diagnosis of WS. Clinical data on the facial features and cardiovascular, endocrinologic, and neurodevelopmental evaluation are presented. The most consistent findings were dysmorphic features (100%), followed by dental anomalies (90%) and hyperacousis (90%). Only eight of 50 children had severe cardiovascular defects that required surgical intervention during the first year of life. Supravalvular aortic stenosis was less frequent (28%) than shown in the literature. Severe hypertension was noticed in 22% of our patients, and infantile hypercalcemia was noticed in 6%. Twelve percent of our patients showed an elevation of CPK. Most children presented with moderate to severe mental retardation with IQ ranging from 20 to 85. Elastin hemizygosity was detected by fluorescence in situ hybridization. Dinucleotide repeat polymorphism analysis was performed in an attempt to correlate phenotype with genotype. The origin of deletions was more frequently maternal (59%), and a more severe phenotype seemed to be associated with those deletions. This is the first report on WS patients in the Greek population.