Recent studies have suggested a similar prognosis for patients with transmural myocardial infarction and nontransmural myocardial infarction despite a smaller infarct size in the latter patients estimated by creatine phosphokinase (CPK). Thirty-one patients with transmural myocardial infarction and 17 patients with nontransmural myocardial infarction as defined by electrocardiographic criteria underwent coronary angiography and left ventriculography from 10 to 24 days after they had an acute myocardial infarction. Forty-three of these 48 patients were asymptomatic following their myocardial infarction. When compared to patients with nontransmural myocardial infarction, those with transmural myocardial infarction had greater peak CPK levels, 1,090 +/- 210 versus 290 +/- 60 IU (p less than 0.01). There was no difference in prevalence of single, double or triple vessel coronary artery disease, mean number of coronary arteries 50 per cent narrowed (2.0 +/- 0.2 versus 2.0 +/- 0.2), near total or total occlusions, coronary score (Friesinger) (7.9 +/- 0.6 versus 8.2 +/- 0.7), left ventricular ejection fraction (48 +/- 2 versus 53 +/- 4), or per cent of akinetic-dyskinetic myocardial segments (66 of 242 [27 per cent] versus 32 of 132 [24 per cent]) between two groups. The similar extent of coronary artery narrowing and degree of left ventricular dysfunction may explain the similar prognosis for patients with transmural myocardial infarction and those with nontransmural myocardial infarction despite differences in enzymatically estimated acute infarct size.