In coronary care units (CCU) without cardiac catheterization facilities, coronary angiography is rarely carried out when a successful medical treatment in the acute phase of unstable angina has been obtained. However, the unstable angina still has an uncertain prognosis when the remission of pain is obtained with drugs. This study presents a follow-up of 147 consecutive patients (aged 66.8 +/- 10.4 years) admitted to our CCU in 1991 and 1992 for unstable angina; 33 of them (22.4%) were in Braunwald class I. 2 (1.4%) in class II and 112 (76.2%) in class III. The patients were treated according to the usual therapy protocols and class III patients received i.v. heparin. In selected cases we used thrombolysis (10 patients) and intra-aortic balloon pump (5 patients). During hospitalization 1 patient died (0.7%), 5 patients (3.4%) suffered an acute myocardial infarction and 9 patients (6.1%) had angina. Stabilization of unstable angina was achieved in 132 patients (89.9%): in 113 (76.8%) during the first 48 hours, and in 19 (12.9%) later. Coronary angiography was carried out in non-stabilized patients and in 46 (34.8%) of the 132 with successful treatment (Group I). Eighty-six patients, without indication to coronary angiography were discharged in medical therapy (Group II). During the follow-up (mean of 15.0 +/- 9.0 months) Group I 10 patients (18.2%) had cardiac events (death, myocardial infarction, or recurrent angina) vs 26 of Group II (p < 0.05). In Group I coronary angiography together with clinical criteria of high risk allowed the identification of candidates to coronary revascularization (61.8% of Group I patients while). These data show that the initial success of treatment during the acute phase of unstable angina should not be considered as a favourable prognostic index. Coronary angiography appears to be indicated for clinical evaluation and therapeutical decision.