Purpose: To report on a vitreous specimen in a 53-year-old patient with unilateral choroiditis and vitritis of unknown cause. Methods: Cytologic examination of a vitreous aspirate strained by the papanicolao method. Results: Intravitreal spirochetes consistent with Borrelia burgdorferi were found in this seronegative patient. Conclusion: Vitreous specimens of patients with choroiditis and vitritis of unknown cause should be examined cytologically, particularly when serologic results do not corroborate the clinical findings of Lyme disease.