Alcohol septal ablation (ASA) causes remodeling of the upper septum and left ventricular outflow tract (LVOT) and reduction in the LVOT gradient. The time course of gradient reduction early after ASA has not been established. This study characterized the time course of gradient response early after ASA. Patients underwent clinical assessment and transthoracic echocardiography at baseline and immediately, 3 days, 3 months, and 1 year after ASA. Forty-seven patients underwent ASA. The baseline LVOT gradient was 98 ± 48 mm Hg. Three-month echocardiographic success, defined as ≥50% gradient reduction from baseline, was achieved in 41 procedures (87%); thus, there were 6 failures. On the basis of percentage reduction in LVOT gradient at 3 days, 2 distinct subgroups of the success group were identified. These were monophasic success (≥50% gradient reduction at 3 days and 3 months, n = 25) and triphasic success (<50% gradient reduction at 3 days but ≥50% gradient reduction at 3 months, n = 16). LVOT gradient in the triphasic success group was similar to that in the failure group at 3 days (81 ± 28 vs 99 ± 31 mm Hg, p = NS) but similar to that of the monophasic success group at 3 months (24 ± 20 vs 12 ± 16 mm Hg, p = NS) and at 1 year (27 ± 24 vs 13 ± 20 mm Hg, p = NS). In conclusion, many patients who undergo ultimately successful ASA demonstrate triphasic LVOT gradient response patterns, with a large gradient 3 days after the procedure.