The territory of the Perm region is highly endemic in Ixodes (B. garinii and B. afzelii)-borne borreliosis. The clinical manifestations of erythema-less Ixodes-borne borreliosis were studied in the 1991-1994 epidemiological seasons. A total of 54 patients were examined in the acute stage of infection and 4-6 months later. There were common symptoms of damage to the central nervous system in early infection and pronounced signs of damage to the central and peripheral nervous systems in the late period which was characterized by cardiovascular diseases as disturbances of automatism functions, conduction, diffuse and local muscle changes.