The demographic features of the dengue cases confirmed during 2001 at the national institute of infectious Diseases, japan, were determined.thirty-five cases were confirmed to be of dengue fever 18 cases were male and 17 female.the youngest case was 19 years old and the oldest was 64 years old.thirty-four cases were determined to be of primary infection, and one was secondary.most of the dengue patients developed illenss after returning from countries in South-East and South Asia.in addition, two patients had visited tahiti and one had visited Samoa before developing dengue fever.dengue fever/dengue haemorrhagic fever is the infectious disease that should attract more attention in japan.