During late summer in 1995 to 1997, repeated outbreaks of maculopapular skin eruptions were observed on legs of children after wading in the pond of the Family Park in Reykjavík, Iceland. Investigation, starting in autumn 1997, revealed that the causative agent was a previously undescribed schistosome cercaria of the genus Trichobilharzia, shed by Radix peregra, the only snail occurring in the pond. This was the first report of swimmer's itch in Iceland. Infection experiments with cercariae from the pond have revealed adult worms and eggs of a Trichobilharzia in the nasal area of ducklings (Anas platyrhynchos f.dom.) 18-23 days p.i., and schistosomula in the spinal cord of BALB/c mice 3, 6 and 10 days p.i. Moreover, a mouse killed 3 days p.i. also had schistosomula in the lungs. During the prepatent period the infected ducklings had neuromotoric symptoms and gross pathology revealed petechiae in the nasal cavity. The results indicate that the cercaria responsible for swimmer's itch in Iceland is a nasal schistosome. Furthermore, adults of two visceral Trichobilharzia species have been found in Icelandic whooper swans Cygnus cygnus. As schistosomula of both nasal and visceral Trichobilharzia species are able to develop and migrate for several days in a non-specific mammalian host, humans are warned to expose themselves to Trichobilharzia cercariae in Iceland.