Doppler echocardiography is a widely used non-invasive method for the evaluation of coronary flow velocities and reserve. We report a case that demonstrates the possible additive role of transthoracic echocardiography (TTE) in the diagnosis of significant left main coronary artery (LM) stenosis in a chest pain patient. Coronary angiography showed no significant LM stenosis. During TTE with pulsed-Doppler measurements, a significant increase in coronary flow velocities could be demonstrated in the distal LM. Intravascular ultrasound confirmed a significant soft plaque in the distal LM. The present case suggests that Doppler TTE may have an additional role in the diagnosis of significant LM stenosis in symptomatic patients. A colour Doppler flow acceleration with high velocities in the LM could raise the suspicion of significant LM stenosis, even if the stenosis cannot be detected by standard coronary angiography.