Background: Endocrine evaluation and long-term follow-up of seven (six male) patients with Williams-Beuren syndrome (WBS) are given. Method: Data were obtained from patients' medical records. All patients underwent hormonal analyses and four of them underwent oral glucose tolerance test (OGTT). Results: They all had mild hypercalcemia. Three of them had overt hypothyroidism while subclinical hypothyroidism was detected in three patients. Four patients had thyroid hypoplasia and one had thyroid agenesis. Growth hormone deficiency (GHD) was determined in one patient. Impaired glucose tolerance (IGT) was found in three adolescents. All adolescents had early-onset puberty. The follow-up duration was 5.7 +/- 2.1 years. The mean growth velocity (GV) was 12.9 +/- 7.2 cm and 7.6 +/- 2 cm at the end of the first and second years of therapy, respectively. All patients had neurodevelopment retardation and were continuing to special education. Conclusions: Thyroid hypoplasia is common and agenesis can be seen in patients with WBS; therefore, thyroid hormones should be measured in the newborn period and annually. GHD should be kept in mind in patients with decreased GV. IGT might be detected in patients with WBS even in adolescence.