Low flow, low gradient aortic stenosis is a highly challenging condition in terms of diagnosis and therapeutic management. With regard to prognosis and to management decisions, it is essential to distinguish those patients with preserved systolic left ventricular ejection fraction from patients with impaired systolic left ventricular ejection fraction, and in particular those with true severe aortic stenosis from patients who have non-significant aortic stenosis associated with reduced transvalvular flow for other reasons and who present with a functionally small valve area. In addition, measurement errors deserve particular consideration in order to avoid a misdiagnosis. Echocardiography, including low dose dobutamine stress studies, is the key diagnostic tool. Magnetic resonance imaging, invasive assessment of haemodynamics by catheterisation and quantification of valve calcification by computed tomography calcium scoring can provide additional information that helps to assess aortic stenosis severity accurately, predict outcome and guide treatment decisions. Percutaneous aortic valve implantation may provide an intervention with lower periprocedural risk in this challenging patient subset; however, further studies are required to define its exact role in this setting.