Objective: This study was planned to evaluate the dynamic left ventricular outflow tract (LVOT) obstruction by using dobutamine stress echocardiography (DSE) in patients with asymmetric septal hypertrophy and/or septal bulging, who have no signs of LVOT gradient detected by conventional echocardiography, with symptoms mimicking hypertrophic obstructive cardiomyopathy (HOCM). Methods: In sixty-one consecutive patients referred to our echocardiography laboratory with HOCM pre-diagnosis, exercise dyspnea and limitation of exercise capacity were evaluated. DSE was performed in 31 patients who fulfilled the inclusion criteria. Patients were divided into two groups according to the degree of dynamic gradient increase above baseline values during stress-test (Group 1 <30 mmHg, Group 2 > 30 mmHg). Left ventricular diameters, septum and posterior wall thicknesses, ejection fraction, LVOT and aortic root diameters, presence of septal bulging and systolic anterior motion (SAM) and degree of septal angulation were sought. Results: There were no significant differences between groups by means of LV diameters, septum and posterior wall thicknesses, EF, LVOT and aortic root diameters, presence of septal bulging (p>0.05); whereas there were significant differences in SAM and degree of septal angulation (p<0.05 and p<0.0001, respectively). Systolic anterior motion 5r=0.61, p<0.0001) and degree of septal angulation (r=0.71, p<0.001) correlated significantly with the dynamic gradient increase. Conclusion: Presence of SAM and degree of septal angulation obtained by DSE are reliable parameters to determine dynamic LVOT obstruction in patients who have asymmetric septal hypertrophy and septal bulging with no gradient on LVOT by conventional echocardiography.