In a prospective study, the relationship between the clinical severity of dengue haemorrhagic fever (DHF) and the sonographic findings was examined. The study comprised 73 cases classified as mild (grades I-II) and 75 as severe (grades III-IV). Ultrasonography in the mild group revealed pleural effusions in 30%, ascites in 34%, gallbladder wall thickening in 32%, hepatomegaly in 49%, splenomegaly in 16%, and pancreatic enlargement in 14%. In the severe group, pleural effusions, ascites and gallbladder wall thickening were found in 95%, pararenal and perirenal fluid collections in 77%, hepatic and splenic subcapsular fluid collections in 9%, pericardial effusion in 8%, hepatomegaly in 56%, splenomegaly in 16%, and pancreatic gland enlargement in 44%. Ultrasound may be useful for early prediction of the severity of DHF in children.