In a prospective evaluation of the safety of short-term observation after elective percutaneous transluminal coronary angioplasty (PTCA) in 1,900 consecutive patients, 1 of 1,680 patients triaged to discharge after 4 hours of observation reached the primary end point of acute recurrent ischemia, 7 patients underwent repeat PTCA during 4 hours of observation, and 66 of 187 patients selected for prolonged observation had a complicated course. It is concluded that short-term observation after elective coronary angioplasty is safe, with a negligible risk of vessel closure after this period; triage for prolonged observation can be based appropriately on the immediate procedural result.