In the suburban and urban forests in the cities of Gdansk, Sopot and Gdynia (northern Poland), Ixodes ricinus ticks should be considered as the vector of pathogenic microorganisms that may cause significant diseases in wild and domestic animals and humans. These microorganisms include etiologic agents of Lyme disease, human anaplasmosis (HA) and babesiosis: Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum and Babesia microti, respectively. DNA extracts from 701 ticks collected in 15 localities were examined by PCR for the simultaneous detection of these 3 pathogens. Overall, 14% were infected with A. phagocytophilum followed by 12.4% with B. burgdorferi s.l. and 2.3% with B. microti. In total, the percentage of infected females (32.9%) was 2.4 times higher than in males (13.7%) and 3.2 times higher than in nymphs (10.3%). Among adult ticks (n = 303), 8.3% were dually infected with A. phagocytophilum and B. burgdorferi s.l., 2.0% with the agent of human anaplasmosis and B. microti and 0.3% with borreliae and B. microti.