All clinical and serologically confirmed cases of sandfly fever among Swedish tourists during 1986-1989 were investigated. A total of 37 cases of Sicilian virus sandfly fever and 1 case of Naples virus sandfly fever were recorded from Cyprus. One case of Toscana virus infection was documented from Spain. The clinical and laboratory findings did not differ from those in previous reports, except for elevated aminotransferase levels. A questionnaire, that offered a possibility to estimate the number of cases that had not been reported, was sent to 713 tourists who had visited different hotels in Cyprus and Mallorca in September 1987. Serum samples from 95 of these tourists were tested for sandfly fever virus antibodies. These tests indicated that only some 20% of the real number of sandfly fever infections had been diagnosed. Both clinical cases and cases found by the questionnaire showed a focal distribution with an overrepresentation of certain hotels in Cyprus. The results were reported to the local health officers and possibly due to the measures undertaken hereafter the number of sandfly fever cases diagnosed have decreased.