Indirect immunofluorescence (II), enzyme-labelled antibodies (ELA), immune blotting (IB) were used for serological evaluation of 74 patients with Lyme disease living in the North-West and Central regions of Russia. Both acute and chronic borreliosis can be seropositive or seronegative. As shown by II and ELA, these patients had a moderate humoral response, high titers of the specific antibodies being a rare finding. The range of anti-Borrelia antibodies (ABA) identified by IB is limited and, as a rule, includes antibodies to no more than 5 proteins of Borrelia burgdorferi. The highest ABA levels were associated with locomotor lesions and were significantly greater of the above levels in patients with migrating erythema. Informative value of II and ELA in Lyme's disease diagnosis according to this study is equal because ELA is more sensitive, while II is more specific. They are both of little help in atypical borreliosis presentation. Most available of other adequate serological tests is IB.