Lyme borreliosis is endemic in the Aland Islands. Exposure of the inhabitants to bites of the tick Ixodes ricinus is heavy. The purpose of this study was to describe symptoms and signs of patients with late Lyme borreliosis in this area, and to correlate the findings with the epidemiological setting. The first 100 consecutive patients with late Lyme borreliosis found in the region since 1984 are included in this study. Neurological, articular and muscular symptoms and signs dominate. General screening for Lyme disease is not recommended in the area due to uncertainty about how to deal with seropositive healthy persons in this heavily exposed population. The recognition and prompt treatment of erythema migrans and other manifestations of primary Lyme borreliosis is important in order to avoid the late stages of the disease. Treatment of all those suffering tick-bites with an antibiotic would be an option in view of the incidence of infected ticks, but cannot be considered because tick-bites are extremely common among the inhabitants. The region would be suitable for general immunization against Borrelia burgdorferi if the means for doing this becomes available in the future.