DHF was common in Cambodia and the rate of admission were 22.1% in total admissionpatients in the hospital in July 2006. The most commonly age group was 5 to 10 years and therewas no significant difference between malesand female, it was similar to the research of LeMinh Khoi which was conducted in Hue City.The significantly clinical signs and symptoms of admission were 68.5%, the incubationperiod longer than one week prior admission was 20.7%, so these cases had disappeared thefever phase and started effervescent phase which was the critical phase of DHF.More than 80%of children had hepatomegaly, abdominal pain andvomiting. PositivehemorrhageandTourniquet testwere 94.6% and91.7%respectively, more common inthe cases withhematemesis and melena.It was difficult to differentiate from intestinal haemorrhage, because most cases had ulorrhgia(from mouth and nose), in which might cause melena or hematemesis. It is a warning sign of The lab results showed the rates ofthrombocytopenia,haemoconcentration andleukocytopenia were88.1%, 29.9% and27.9%respectively. Especially, 63 serious cases hadthrombocytopenialess than 50G/L.Comparing DHF toDSS group showedthat DSS occurred more common inyoungerchildren. Specifically, in 28 cases with DSS, five cases were under one year and eightcaseswereunder oneyear with DHF and 5 cases withshocksyndrome.Most of research showed there were few childrenunder oneyearhaving DHF, whilethere wasadifferencein this study and it might be a characteristic of DHF in Cambodia.Thesigns and symptomsincludinginternal haemorrhage, vomit andhepatomegalyshowed higherproportionthan other countries. Theincrease ofhaemoconcentrationand decrease of plateletcounts in DSS showed moremuch severe than DHF. Similar to other studies, the above factorswere the risk factor developing to shock of DHF.Accordingto Tram et al, dengue patientswith internal haemorrhagehad muchlongerandsevereshockthan patients without internal haemorrhage, in which is56.7% to 12.6%.WHO alsoalertedthat the childrenunder one yearwith risk factorssuch as low weight, internalhaemorrhage, changing of mental status, prostration or coma, history of asthma, congenital heartdisease or G6PD deficiency should get critical care.Vuth et al(2004)gave that risk factors of shock in DHF weretheincrease ofhematocritupto 45%, internal haemorrhage, abdominal pain and the decrease of platelet less than 50 G/L.Khoi et al showed that the haemoconcentration, leukocytopenia and thrombocytopeniawere related to the severe grade of DHF.However, eight patients under one year and five cases with shock were not related to therisk factorsas those authorsdescribed.Allfive children had no increase ofhematocrit;only onepatient had low platelet below 50 G/L. Although the samples were small, children less than oneyear should be receivedcritical care, because this age group can developto shock quickly withnonspecific signs and symptoms.