The aim of the present study was to determine the seasonal abundance of ticks, Ixodes ricinus and their infection frequency with spirochetes, Borrelia burgdorferi in wooded areas of the vicinity of the city of Szczecin during 2000-2001. The ticks were collected from April to October. Presence of Borrelia burgdorferi sensu lato was detected with the method of indirect immunofluorescence (IFA). The results showed differences in seasonal activity of ticks within the years of the study. In the year 2000 a single peak of their increased activity was noted, while in the year 2001 no significant changes in the population of Ixodes ricinus were recorded. Borrelia burgdorferi s. l. was detected in 2000 and 2001 in 11.6% and 9.6% of the specimens captured, respectively, which constituted a statistically significant difference. The highest level of infection of Ixodes ricinus in 2000 was observed in April (13.2%), while in 2001 - in July (12.7%). The differences in the prevalence value between respective months of both years were not statistically significant. The results of the present study indicate a high risk factor of acquiring Lyme borreliosis by humans and animals in wooded areas of the Szczecin vicinity.