Serologically confirmed cases of dengue fever among Swedish tourists were studied retrospectively. Dengue fever was found to be the most commonly diagnosed imported arbovirus disease in Sweden during the period December 1989-November 1990. 24 cases were diagnosed. The geographical epidemiology showed that 17/23 who answered a questionnaire were infected in Thailand, most often during spring and early summer. 17 patients were admitted to hospital. All patients had high fever. Other common symptoms were myalgia, headache, fatigue/prostration and erythema. All patients but 1 with a long-standing ataxia recovered without sequelae. Low white blood cell and platelet counts were registered in all sampled patients. Depressed sodium levels and elevated liver enzymes were seen regularly. Dengue virus type 1 was isolated from 2 patients who suffered from dengue haemorrhagic fever grade II in the course of their primary dengue virus infection.