During the period between 1988-1989 529 cases of Lyme borreliosis were reported to the hygiene service of the West Bohemian region. Of these 164 (31.0%) were confirmed by indirect immunofluorescence. 342 (64.6%) patients reported contact with a tick, another 108 patients reported contact with other arthropods. Among the affected systems the skin and nervous system predominated. From the total number of 443 cases of erythema chronicum migrans the aetiology was confirmed serologically in 84 (19.0%). Comparison of skin diseases confirmed and not confirmed by laboratory tests, classified by age, sex, monthly incidence and contact with arthropods revealed that the clinical diagnosis of skin symptoms of Lyme borreliosis in the West Bohemian region is of a high standard.