OBJECTIVE The aim of the present study was to evaluate maximal longitudinal relaxation velocity of the left ventricle as an index of diastolic function. DESIGN Sixty-four consecutive patients with known or suspected heart failure, referred to echocardiography, were investigated by M-mode recordings and pulsed tissue Doppler recordings of the maximal early diastolic velocity of the mitral annulus. The classification as true positive or true negative cases was done using age-related reference values of mitral inflow and pulmonary vein flow. RESULTS A rather high sensitivity of 89% was found for M-mode recordings and a slightly lower sensitivity of 81% for pulsed tissue Doppler recordings. A moderate high specificity was found: 81% for M-mode recordings and 78% for tissue Doppler recordings. The velocities recorded by pulsed tissue Doppler were about 30% higher than velocities recorded by M-mode. CONCLUSION Maximal relaxation velocity in the long axis of the left ventricle, recorded by either M-mode or tissue Doppler, can be used for assessment of diastolic function but reference values cannot be used interchangeably.