The aim of this study was to determine the prevalence and clinical characteristics associated with stress Hyperglycemia among patients attending to the neonatal and pediatric Emergency wards. Patients who require d blood sampling for evaluated of an acute illness from August 1995 to July 1996 to the Namazi hospital of Shiraz medical university were enrolled prospectively for Hyperglycemia ( plasma glucose>150 mg/ DL). A total of 1620 patients ranging from 3 days to 16 years were enrolled. Plasma glucose values ranged from 29 mg/ DL to 593 mg/ DL. 206 patients (12.7℅) had Hyperglycemia. The prevalence of stress Hyperglycemia was significantly higher among patients if they: 1. Were neonates and infants <2 year (20.22℅) versus older children 2_6 year ,(9.8℅), 6_12 year (3.25℅) and adolescents 12_16 year (5.1℅) ( p<0.001). 2. Had acut illnesses (27.2℅) versus more chronic disease (6.8℅) ( p<0.001). 3. Several dehydrated (75.9℅) versus not several dehydrated (10.4℅) ( p<0.001).4. had convulsions in their recent illness (29.7℅) versus not having convulsions (8.5℅) ( p<0.001). 5. Had vomiting and diarrhea in recent illness (40.3℅) versus not having vomiting and diarrhea (9.1℅) ( p<0.001). 6. Had unstable vital signs (44.3℅) versus stable vital signs (7.5℅) ( p<0.001).7. had been admitted to an intensive care unit, neonatal ICU (80℅), pediatric ICU (62.5℅) and neonatal Emergency room (21.8℅) ( p<0.02). It is concluded that stress Hyperglycemia is a frequent clinical occurrence in a pediatric emergency departments, and it does not appear to be specifically associated with any particular disease but is significantly related to the severity , acuity of the illness and state of hydration of the patient.