A clinicopathological study of the 1972-1973 A2 England influenza epidemic is presented. In fatal cases early necrosis of myofibrils was present in those patients who died within 24 hours of the onset of the influenza symptoms. At 5 days gross changes were present. These were largely resolved by the eighteenth day of illness. In 42 patients treated at home, transient ECG changes were found in 18 cases. These included ST-segment deviation, T-wave inversion, flattening of the T wave, sinus bradycardia, sinus tachycardia, nodal rhythm, and atrial fibrillation. Permanent changes were observed in one patient and in an additional patient admitted to hospital with permanent A-V block.