In Bucaramanga, Colombia, dengue haemorrhagic fever (DHF) has become endemo-epidemic since 1992. A cross-sectional study covering a period of 10 years (February, 1992 to February, 2002) was undertaken in children under 13 years of age hospitalized at the University Hospital. Observations were recorded on the clinical features, laboratory tests and the natural development of the disease. A total of 763 patients were examined, of whom 617 were classified as having DHF according to the WHO criteria (9.1% Grade I, 61.5% Grade II, 21.7% Grade III and 7.5% Grade IV). One hundred forty six patients could not be classified. The highest incidence took place in 1997, 1998 and 2001. Seventy four per cent of patients came from the metropolitan area of Bucaramanga; 48% were males; 0.3%, newborns; 11.8%, infants; 23%, pre-school children, and 64.9%, school children. The most important clinical features were fever and haemorrhagic manifestations (100%); vomiting (60%); abdominal pain (57%); headache (50%); osteomyalgia (40.8%); hepatomegaly (33%), and macular rash (29%). Among the haemorrhagic manifestations we found petechiae (56%); positive tourniquet test (35%); gastrointestinal bleeding (34%), and epistaxis (32%). Serous effusion was found in 17.7% of cases. Alarm signs of shock were found in 29%. Fifty two per cent had leucopenia and 37.3% atypic lymphocytes. Among other unusual manifestations were hepatitis, encephalopathy, alithiasic cholecystitis, acute renal failure, haemophagocytic syndrome and coinfections. Of the 617 cases, 12 died (1.5%).