In 1984, two human cases of tick-borne Lyme borreliosis with considerable neurologic involvement were reported in Berlin (West). The diagnosis of Lyme borreliosis was serologically confirmed. The ticks which had transmitted the Borrelia were from Berlin (West). In the autumn of 1985, 156 ticks were collected in forests of Berlin (West) for the cultural detection of spirochetes by using BSK II medium. Three strains of spirochetes were isolated (from a pooled sample of two nymphs, and samples of one nymph and one female tick, respectively). These isolates were identified as Borrelia burgdorferi by means of SDS-PAGE, Western blot (using monoclonal antibody H 5332), microscopic agglutination test and electron microscopy. Investigations with the electron microscope showed that cells of two isolates (strains 2/B45 and 3/B56) had 8 flagella inserted at each end. The cells of the third isolate (strain 1/B29) had 9 flagella inserted at each end. This type had not been observed before.