This thesis used tissue Doppler echocardiography to characterise, in detail, left ventricular function in 1006 subjects and produced several novel findings. Firstly, transmitral Doppler had limited ability to identify impaired diastolic function in a cohort at high risk of diastolic dysfunction. Further, the Valsalva maneouvre was found to be unreliable as a discriminator in subjects with an apparently normal transmitral Doppler flow profile. Secondly, using tissue Doppler early mitral annular velocities (E'), subjects of African- Caribbean ethnicity were demonstrated to have more impaired diastolic function than populations of White European origin. Thirdly, a correlation was demonstrated between fasting plasma glucose levels and left ventricular diastolic function, supporting the concept of a 'diabetic cardiomyopathy'. Fourthly, the anti-hypertensive combination regimen atenolol+/- bendroflumethiazide was demonstrated to be associated with relatively adverse measures of diastolic function when compared to a regimen of amlodipine+/- perindopril. Finally, a large cohort of hypertensive subjects underwent echocardiography and was followed for 4.2 years. The strongest predictor of future cardiac events proved to be the subject's diastolic function, as measured using the ratio of the transmural pulsed Doppler early filling velocity (E) to the tissue Doppler early mitral annular velocity (E'). Three of the chapters in this thesis formed the basis for publications in major cardiac journals, as described at the outset of this thesis. One of the aims of this body of research was to provide further support for the inclusion of Tissue Doppler echocardiography in standard clinical echocardiographic protocols. This is now the case, with most echo labs including TDE measures in their routine studies as a result of the large body of work now existing in the literature, of which this thesis forms one small component. The non¬ invasive assessment of left atrial filling pressure using the E/E' ratio is now routinely quoted in the average echocardiographic report and the data reported in this thesis add further focused support for that strategy.