67Ga scintigraphy was performed in a patient with fever of unknown origin. Left pneumonectomy had been performed two years previously for carcinoma of the lung. There were no cardiovascular or new pulmonary signs. Four weeks of in hospital investigation did not reveal the cause of the fever. 67Ga uptake was localized in the heart and subsequent autopsy demonstrated pericardial metastasis to be the cause of the prolonged fever. Fever of unknown origin is a rare presenting symptom of malignant pericardial involvement and 67Ga scintigraphy was crucial in its diagnosis.