Different techniques have been developed to aid in laboratory diagnosis of Lyme disease. The detection of serum antibodies, in particular, is relied on heavily by the medical community and is currently the most practical means of confirming B. burgdorferi infections. Although most assays may not detect low amounts of IgM antibody during the initial weeks of infection, application of a capture ELISA method has been reported to improve test sensitivity. Antibodies to Borrelia and Treponema spirochetes will cross-react in conventional assays being used for Lyme disease, but in most cases, these problems can be eliminated by performing other serologic tests or by reviewing clinical and epidemiologic data. Further improvements in the laboratory diagnosis of Lyme disease should be made by standardizing current methods (including commercial test kits), establishing reference laboratories in the United States and Europe, and by developing rapid antigen detection procedures. Finally, serologic determination of B. burgdorferi infections should remain secondary to clinical diagnosis.