To report retrobulbar neuritis caused by Borrelia afzelii culturally proved from cerebrospinal fluid (CSF).A 23 year old female underwent ophthalmologic, laboratory and other auxilliary examinations.CSF cultures grew spirochetal microorganisms, serotyped by monoclonal antibodies as Borrelia afzelii. Following the serological and cultural results, treatment with doxycycline 200 mg daily was started and kept for three weeks. Gradual improvement of the visual acuity of the right eye was observed with full recovery to 20/20.Borrelia infection should be considered in the differential diagnosis of retrobulbar neuritis. CSF should be examined also culturally. (Ref. 5.)