A case of malignant lymphoma associated with complete heart block in a 30-year-old woman is reported. The patient progressively deteriorated despite temporary pacing and died 24 days after being admitted. Microscopic examination of the heart revealed marked infiltration by lymphoma cells in the atrioventricular node and the bundle of His. A diffuse lymphoma (large cell type, B cell) was diagnosed. This case is considered to be rare, since complete heart block was the first and only manifestation of the malignant lymphoma.</p
