Indications for electrical pacing were present in 58 of 665 patients with acute myocardial infarction (8.7%). Posterior-wall infarction had occurred in 34, anterior-wall infarction in 20, while two had combined infarction and in a further two precise localisation was not possible. There were 16 deaths (27.6%), six of them with posterior-wall and nine with anterior-wall infarction. Bradycardic arrhythmias with A-V block predominated among posterior-wall infarctions, hemiblocks and bifascicular block in anterior-wall infarctions. Permanent pacing was practised in 14 patients, 11 with posterior and three with anterior-wall infarctions, i.e. permanent pacing was four times as common after posterior than anterior-wall infarctions, the proportion being 2:1 for temporary pacing, largely due to a higher mortality-rate after anterior-wall infarction. Old anterior-wall scars were present in nine of eleven patients with permanent pacing. Because of the danger of late bradycardia or A-V block patients with posterior-wall infarction should be carefully followed in the late phase (from about the third week onwards), especially if it is known that they have an old anterior-wall infarct.