Doppler left ventricular inflow time-velocity curves have been extensively used to evaluate left ventricular filling. The reproducibility of the technique, however, has been rarely assessed, its temporal variability being, presently, unknown. In order to define the temporal reproducibility of Doppler parameters of left ventricular filling, 10 normal subjects were studied at 3 different times (baseline, after 24 hours, and after 1 week). No parameter changed significantly during 1 week follow-up. When variability, however, was expressed as percent changes relative to baseline, values ranging from 5.7% to 25% were found, the largest variability being associated with acceleration-deceleration parameters (p less than 0.001). In conclusion temporal variability of parameters obtained from Doppler diastolic mitral time-velocity curves is acceptable in homogeneous groups of subjects. When the technique, however, is used for serial evaluation of ventricular filling in a single patient, the specific temporal variability of the parameter considered must be taken into account before any variation can be ascribed to real hemodynamic changes.