Blood samples from 160 inhabitants of the Republic of Bangladesh were studied by haemagglutination inhibition (HI), indirect HI, and radial haemolysis in gel tests. The sera were found to contain antibodies to the arborviruses of Sicilian (6.25%) and Naples (1.25%) sandfly fevers and to the Karimabad virus (11.25%) which are transmitted by Phlebotomus papatasi. Antibodies to the Karimabad virus were found among the Bangladesh population for the first time.