Our earlier studies on ticks, Ixodes ricinus have demonstrated that the north-western part of Poland is an endemic area for Borrelia burgdorferi sensu lato and therefore sick dogs, at the time of the highest activity of ticks, should be suspected for having borreliosis. We carried out a preliminary PCR survey of the blood of 15 dogs naturally exposed on ticks for the presence of the DNA of B. burgdorferi using primers complementary to the fragment of the gene encoding 16S rRNA of the small ribosome subunit. We found 6 out of 15 dogs were infected, although 2 dogs had a lameness - the attribute of canine borreliosis were PCR-negative. Our findings suggest that the exposure to B. burgdorferi is common in dogs in the region declared an endemic area of borreliosis, and that this disease should be important to local veterinarians.