Dengue virus infection may remain asymptomatic or manifest as nonspecific viral infection to life threatening dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS). Patients with DHF/DSS have fever, hemorrhagic manifestations along with thrombocytopenia and hemoconcentration. Thrombocytopenia and hemoconcentration are distinguishing features between DHF/DSS and dengue fever (DF). Some patients with dengue fever may have significant bleed and mild thrombocytopenia but no hemoconcentration. These patients are labelled to have dengue fever with unusual bleeds. Laboratory findings in DHF/DSS include rising hematocrit, thrombocytopenia and transformed lymphocytes on peripheral smear. There may be increased transaminases, hyponatremia, transient increase in blood urea nitrogen and creatinine. In severe disease there may be lab evidence of dissemination intravascular coagulation. X-ray film of the chest may show pleural-effusion. Ultrasonogram of abdomen may detect thickened gall bladder wall with hepatomegaly and ascitis. In some patients there may be abnormality in electrocardiogram and echocardiogram. The diagnosis of DHF/DSS is based on typical clinical findings. For confirmation of dengue virus infection viral culture can be done on blood obtained from patients during early phase of illness. In later part of illness antibodies against dengue virus can be demonstrated by various techniques. The treatment of DF is symptomatic. For control of fever nonsteroidal anti-inflammatory drugs should be avoided. DHF/DSS are managed by intravenous fluid infusion with repeated monitoring of vital parameters and packed cell volume (PCV).