Between June 1988 and July 1991, 464 new device interventions (Palmaz-Schatz stent or Simpson directional atherectomy) were performed in 410 patients. Chest pain occurred within 72 hours after the procedure in 94 patients (23%). All patients were evaluated with electrocardiograms and cardiac isoenzymes on the day after the procedure, and urgent repeat coronary angiography was performed in 29 chest pain patients (31%). Whereas all 14 patients with abnormal findings on repeat angiography had electrocardiographic changes, 6 of the 20 restudied patients (30%) with electrocardiographic changes had no angiographic explanation for chest pain. Non-Q-wave myocardial infarction occurred in 22 patients (5%) (10 of 35 [29%] with chest pain and electrocardiographic changes, 3 of 44 [7%] with chest pain and no electrocardiographic change, and 9 of 316 [3%] without chest pain). Factors associated with chest pain after new device intervention included a decreased residual percent stenosis (p = 0.05), incomplete revascularization (p = 0.005) and the presence of multivessel disease (p = 0.001). Vessel dissection after stenting but not atherectomy was associated with postprocedure chest pain. Chest pain is common (23%) after new device intervention. Electrocardiographic changes are a sensitive marker of angiographic abnormality and confer a higher risk of non-Q-wave myocardial infarction, but no increase of in-hospital mortality. Determinants of postprocedure chest pain are lower residual percent stenosis, incomplete revascularization and the presence of multivessel disease. Patients with chest pain but no electrocardiographic changes early after successful stent placement or atherectomy need not routinely undergo urgent recatheterization.