BACKGROUND: Enhanced external counterpulsation (EECP) is a noninvasive treatment of patients with refractory angina. The immediate hemodynamic effects of EECP are similar to intra-aortic balloon pump counterpulsation, but EECP's effects on standard blood pressure measurements during and after treatment are unknown. METHODS: We evaluated systolic blood pressure (SBP) and diastolic blood pressure (DBP) for 108 consecutive patients undergoing EECP. Baseline SBP, DBP, and heart rate were compared for each patient before and after each EECP session, at the end of the course of EECP, and 6 weeks after the final EECP session. RESULTS: One hundred eight patients (mean age 66.4 +/- 11.2 years, 81% male) completed 36.5 +/- 5.1 EECP sessions per patient. Overall, based on 3,586 individual readings, EECP resulted in a decrease in mean SBP of 1.1 +/- 15.3 mm Hg at the end of each EECP session (P < .001), 6.4 +/- 18.2 mm Hg at the end the course of EECP (P < .001), and 3.7 +/- 17.8 mm Hg 6 weeks after the final EECP session (P = .07), with no significant change in DBP or heart rate. Stratifying by baseline SBP, a differential response was demonstrated: SBP increased in the 2 lowest strata (<100 mm Hg and 101-110 mm Hg) and decreased in the remaining strata (P < .001). Stratified differences were sustained after individual EECP sessions, at the end of the course of EECP, and 6 weeks after the final EECP session and were independent of changes in cardiovascular medications. CONCLUSIONS: Enhanced external counterpulsation improved SBP in patients with refractory angina. On average, EECP decreased SBP during treatment and follow-up; but for patients with low baseline SBP (<110 mm Hg), EECP increased SBP. The improvements in SBP may contribute to the clinical benefit of EECP.