The presence of anti-IgG antibodies in sera of dogs from eastern Slovakia (urban agglomeration of Kosice) was determined by ELISA and Western blotting. Various B, burgdorferi sensu late strains of different genospecies and geographical origin were used in these assays: Slovak strains Ir105 - B, burgdorferi s.s. and K24 - B. garinii; American strain B31 - B, burg dorferi s.s.; Swiss strains NE462 - B. garinii and NE632 - B. afzelii. Seropositivity in ELISA depended on the strain used and varied from 25.9% with strain B31, to 48.1% with strain K24 and 48.1% using strain Ir105. Sera from 13 dogs (44.4%) showed consistent positive and negative results in ELISA with three above mentioned strains. Using endemic strain - local isolate Ir105, 85.18% (23 out of 27 sera examined) agreement between ELISA and Western blotting was obtained. The study included the comparison of immunoblot patterns of dog sera with four strains of B. burgdorferi. Intense bands were detected for the 93-, 60-, 45-, 56-, 45-, 41-, 39-, 31-, and 24-kDa antigens. Compared with geographically distant strains, dog sera reacted with a higher number of borrelia proteins when endemic strains (B. burgdorferi s.s. and B. garinii) were used.