Vector-borne diseases constitute more than 17% of total number of infectious diseases being caused by a multitude of environmental and social factors. The literature contains updated information on the increasing number of pathogens transmitted by ticks (Acari, Ixodidae), for example in Germany in the last 15 years have been reported at least eight new agents pathogenic or potentially pathogenic to humans, including several species of Borrelia, Rickettsia and Anaplasma. Studies in Moldova have determined in the ixodid tick population the presence of causative agents of acarian encephalitis, infection with West Nile, Lyme borreliosis, ehrlihiosis, babesiosis, anaplasmosis, bartonellosis, ricketsiosis and tularemia. Currently, according to statistics the most common vector-borne disease in the country is Lyme borreliosis. Long-term study of the vectors ecology is important for emphasize the changes in the correlation between “pathogen agent – specific vector – receptive host”, especially in the context of climate change from the last decades, the expansion of the phenomena of migration and urbanization of new territories, which what contributes to the risk increasing of transmission of pathogens to humans by ixodid populations. During spring, summer and autumn periods of 2012-2015 962 specimens of ixodid ticks were collected from various natural and anthropogenic ecosystems of Chişinău city, given the peculiarities of their habitats and preferred spreading area. Field works were carried out in 32 points of annual and multiannual monitoring, using the “Flag” method. The species and the sex of collected ixodid specimens were determined. For the presence of Borrelia in the hemolymph and intestine contents 616 adult individuals of ixodid tick were examined. The index of species population density was calculated, as well as dominance and the rate of ixodid contamination with Borrelia, their diversity and territorial spread were determined. Data on the incidence of Lyme borreliosis in Chisinau city for 2012-2015 were obtained from the Statistical Report “Infectious and parasitic diseases.” Chisinau city is located at 47.0122 N and 28.8605 E and covers an area of about 120 km2. The faunistic material was collected in natural and anthropogenic ecosystems in the city (Buiucani, Ciocana, Riscani, Botanica districts) and suburban municipality (Vadul lui Voda town, Dobrogea and Hulboaca villages). 83 routes were taken of 200m each. In the reference period 5 species of ixodid ticks were identified: Ixodes ricinus (41.9%), Dermacentor marginatus (32.4%), D.reticulatus (19.4%), Haemaphysalis punctata (3.5%) and H.inermis (2.7%). In most studied habitats of annual and multiannual monitoring a diversity of 2-4 species was registered. I. ricinus is the most common species of ixodid, recorded almost in all the researched habitat, thus presenting the highest epidemiological significance in terms of borreliosis circulation in nature. Mean index of I.ricinus tick density was 4.8 mature individuals per 200 m route, D.marginatus - 3.7 D.reticulatus - 2.2, H. punctata and H. inermis - 0.4 and respectively 0.3 adult individuals per 200 m route. A large number of ixodid ticks was recorded in areas of recreation and leisure near water basins with much vegetation from Ciocana and Buiucani (Sculeni district) constituting 53 and 38 individuals respectively, in the forest belts of Riscani, Ciocana, Vadul-lui-Voda town, Hulboaca vill. from 12 to 40 individuals, in summer camps for children located in forest from Vadul lui Voda town from 4 to 39 individuals per 200 m route. Microscopic studies for Borrelia identification have revealed that the percentage of infected ticks in 2015 and 2012 was the highest, constituting 36% and 34% respectively, compared to 2014 (22%) and 2013 (21%). Cases of Lyme borreliosis illness in humans in Chisinau city are recorded annually since 2000, including in 2015 - 97 cases, in 2014 – 59, in 2013 – 65, while in 2012 the highest number of disease cases have been reported – 117. In annual dynamics springsummer seasonality of the disease was attested, corresponding to the period of maximum biological activity of ticks. At the same time the true incidence of Lyme borreliosis remains underestimated due to low alertness of population on the risks associated with tick bite and low number of doctor visits to diagnose the disease. We conclude that in natural and anthropogenic ecosystems of Chisinau city five ixodid species were identified, the dominant species being I. ricinus. The presence of vectors – Ixodid ticks on the territory of Chisinau, as well as the intense movement of Borrelia in ticks maintain the high risk of occurrence of Lyme disease cases in the human population.