Co-occurrence of granulocytic anaplasmosis, borreliosis and babesiosis in humans is a result of common vectors for the respective pathogens of these diseases, most commonly ticks from the genus Ixodes. Studies on ticks in Europe and also in Poland have shown that several pathogens may co-occur in individuals of I. ricnus. A total of 96 hospitalised patients infected or suspected of being infected with borreliosis were screened for A. phagocytophilum and Babesia sp. DNA. Positive results of PCRs for A. phagocytophilum DNA were obtained for 10 patients, 8 of whom were diagnosed with borreliosis earlier, and 4 of whom were diagnosed with tick-borne encephalitis (on the basis of serological studies of serum and cerebrospinal fluid). None of the 10 patients had clinical or biochemical markers of anaplasmosis, corroborating the existence of asymptomatic anaplasmosis or self-limiting course. in Europe. Similarly, Babesia DNA was not found in the blood of any of the patients. The results of the studies show that in diagnosing tick-borne diseases, clinical examinations should consider infection by two or even three tick-borne pathogens.