Background/Aims: Borrelia burgdorferi spirochete has been found both in bladder biopsies and the urine of patients with Lyme disease (LD) as well as in experimental animals. The urological symptoms in borreliosis resemble those of interstitial cystitis (IC): frequency, urgency and nocturia. The aim of this studies is to find the role of B. burgdorferi in interstitial cystitis.Methods: We studied antibodies against B. burgdorferi from serum samples of 50 IC patients with two separate EIA tests. Patients with positive serology in both tests underwent cystoscopy and a bladder biopsy was taken. The presence of borrelia DNA was studied with borrelia–specific polymerase chain reaction (PCR), and with universal bacterial PCR.Results: IgM class antibodies to B. burgdorferi were not found, but IgG antibodies were found in four samples (8%). This was higher than in the control material (2%). One patient’s sample was strongly positive, whereas three samples were weakly positive. Bladder biopsies taken from the 4 patients were negative for borrelia DNA in both PCR tests. None of the seropositive patients had any symptoms consistent with LD.Conclusion: These results indicate that persistent infection of B. burgdorferi has no role in the etiology of IC. On the other hand a connection with a past borrelia infection and IC is not excluded.