The purpose of the investigation was to chart the existence and extent of arboviruses in Norway and provide information on their possible significance. Virus isolations have been attempted from ticks (I. ricinus, I. trianguliceps, I. uriae) and host animal blood from selected locations. Serological screenings have been performed with bird, small mammal, cattle and human blood. Five virus strians have been identified to date. Three of them are related to Uukuniemi virus group. Two identical strains from I. uriae demonstrate the morphology of coronaviruses and no antigenic relationship to major arbovirus groups. Within the distribution areas of I. ricinus, antibodies to tick-borne encephalitis virus are prevalent in cattle. Antibodies to Uukuniemi viruses are found in passerine birds, small mammals, cattle and man. Antibodies to the coronavirus like agents have been demonstrated in seabirds.