In Europe, of all the vector transmitted diseases, the occurrence of lyme disease is the one most often registered, and the most significant vector Borrelia burgdorferi is the tick Ixodes ricinus. Both humans and animals contract lyme disease. The risk of the occurrence of lyme disease is in correlation with potential exposure to tick bites and depends on the density of the tick population in the endemic area, the percentage of ticks infected with the cause of lyme disease, the duration and the nature of the activity of the susceptible population in a certain area. The objective of these investigations was to determine the entomological and the ecological risk index, as well as to assess the risk of transmission of the cause of lyme disease in the territory of Vojvodina Province in the Republic of Serbia. Ticks were collected at 12 locations in the South Backa District of Vojvodina. A total of 1400 ticks were identified up to the level of species. After establishing the infection of ticks with the cause of lyme disease, the entomological and the ecological index was determined for the given regions using microscopic examination in a dark field. Two species of ticks aere identified in this geographic region (Ixodes ricinus and Dermacentor marginatus). Examining I. ricinus, the prevalence of infection B. burgdorferi was established, ranging up to 33.1%. The ecological risk index indicates that there is a potential risk of humans and animals becoming infected at 8 localities. It was determined for 3 localities that there is a definite actual risk of the transferrence of causes of lyme disease.