Selected, highly specific antibodies to B. burgdorferi proteins are commonly used in diagnostic serological tests for Lyme disease. From the point of view of diagnosing Borrelia burgdorferi infection, highly immunogenic antibodies to some proteins detected in vivo after B. burgdorferi transmission to the host human body seem to be very significant. Knowledge on importance of proteins that are expressed in vivo alone has accumulated recently. The proteins are: VlsE, BBA36, BB0323, Crasp3 and pG. The main goal of this study was to evaluate the presence of IgM and IgG antibodies against expanded panel of Borrelia burgdorferi specific antigens, including antigens that are expressed in vivo alone. The study was conducted in the group of 25 patients diagnosed with borreliosis, hospitalized in The Department of Infectious Diseases, Medical University of Lublin. The diagnosis of borreliosis was based on patient’s history, clinical symptoms and ELISA serological test results. Testing for IgG and IgM antibodies to Borrelia burgdorferi was performed using Immunoblot (Genzyme Virotech) which included antigens for IgM: OspC, p39, EBV-VCA-gp 125; for IgG: VlsE, p39, p83, BBA36 (iv1), BBO323 (iv2), Crasp3 (iv3), pG (iv4). In that group IgG antibodies against full antigens panel VlsE, p39, p83, BBA36 (iv1), BB0323 (iv2), Crasp3 (iv3), pG (iv4) were observed in 3 patients (12%). In 12 patients (48%), in addition to IgG against VlsE, p39 and p83, antibodies against BBA36 (iv1), BB0323 (iv2), Crasp3 (iv3), pG (iv4) were detected with various frequency. The remaining 10 patients (40%) tested IgG positively based on presence of VlsE and/or p39, p83. In spite of long term infection, the results revealed the presence of IgM antibodies against OspC and p39 – 16 tested patients (64%), against OspC – 5 tested patients (20%), against p39 – 1 tested patients (4%). We conclude that: 1. IgG antibodies to VlsE (antigen from in vivo group) are the most frequently produced during borrelia infection. 2. Membraneous proteins: p39 and p83 present in diagnostic serologic tests are reliable markers of B. burgdorferi infection. 3. In vivo proteins alone used in diagnostic tests do not guarantee reliable results that either would confirm or exclude B. burgdorferi infection.