In 50 normal subjects and in 63 patients with ischaemic heart disease, the left ventricular apexcardiogram with its first derivative (dA/dt), electrocardiogram and phonocardiogram were recorded simultaneously. This allowed to measure four systolic and diastolic time intervals using the first derivative of apexcardiogram. In patients with ischaemic heart disease in increase of the interval R to peak dA/dt, systolic upstoke time of dA/dt, and early apexcardiographic relaxation time (the time from the onset of the aortic component of the second heart sound in the phonocardiogram to the negative peak of the dA/dt) was established. It is concluded that dA/dt is a suitable technique for more exact non-invasive determination of some time intervals than conventional apexcardiogram in ischaemic heart disease.