A 31-year-old man who had been under regular hemodialysis for 6 months was 
diagnosed as Williams syndrome (WS) by fluorescence in situ hybridization (FISH) 
chromosomal analysis. The association of WS and chronic renal failure (CRF) is 
only rarely encountered. Endocrinological examinations revealed 
hypergonadotropic hypogonadism. Prolonged and exaggerated responses of 
adrenocorticotropin (ACTH) to insulin-induced hypoglycemia and corticotropin 
releasing hormone (CRH) were also noted. While most of the endocrinological 
abnormalities observed in this patient could be attributed to altered endocrine 
circumstances in CRF, some findings stand in contrast. Furthermore, the 
testicular biopsy specimen showed severe hypospermatogenesis. Endocrine 
disorders observed in this patient may be at least in part, responsible for 
various clinical features underlying WS.