Tuberculous lymphadenitis that had developed after treatment with systemic prednisolone was diagnosed using the polymerase chain reaction (PCR) combined with dot-blot hybridization. Although the patient had no history of tuberculosis or suggestive radiological findings, a DNA fragment specific for Mycobacterium tuberculosis complex strains was amplified from a paraffin-embedded biopsy specimen of a cervical swelling, which was compatible with tuberculous lymphadenitis on haematoxylin-eosin (HE) and Ziehl-Neelsen staining. This report demonstrates the practical use of PCR for diagnosis of extra-pulmonary tuberculosis in a case difficult to diagnose conventionally.