This thesis deals with Lyme borreliosis, an infectious disease which occurs worldwide and is the most common thick-borne disease. It is a disease caused by a mikroorganism called Borrelia burgdorferi and other human pathogenic genera belonging to the Borrelia burgdorferi complex. The aim of this thesis is to evaluate a serologic test from bioMérieux, the VIDAS Lyme IgM and VIDAS Lyme IgG Assay, and its use in a routine microbiology laboratory as a tool in diagnosing Lyme borreliosis. This Assay combines a two-step en-zymeimmunoassay-sandwich-method with a fluorescent detection and detects both, IgM and IgG antibodies. This thesis concentrates on the specificity and cross reactivity of the VISA Lyme assay. In total, 158 serum samples have been tested and after a careful eval-uation it is proven that this serologic test has a specificity of 94,63% and a cross reactivity of 13,33%.