The laboratory diagnosis of Lyme disease in Denmark is reviewed with recommendations for serological testing. In Denmark the laboratory testing is performed with an ELISA technique. Most laboratories use an assay based on purified flagella antigen. The two-tier approach with Western Blot as confirmatory testing is not recommended since the contribution to the diagnostic specificity is only marginal. Predictive values of Lyme serology are presented, based on the estimated prevalence of the different stages of Lyme disease in Denmark.