Color tissue Doppler (TD) measures mean myocardial velocities, whereas spectral TD measures peak velocities. Given that most data on left ventricular (LV) diastolic function used spectral TD, we investigated whether the differences in myocardial velocities between these modalities resulted in discrepancies in calculated E/Ea.Patients were imaged using an ultrasound machine. The systolic (Sa), early diastolic (Ea), and late diastolic (Aa) myocardial velocities by color and spectral TD were measured at basal and midsegments of the LV septal, lateral, inferior, and anterior walls in the apical views. The average of basal septal and lateral Ea was combined with the early transmitral diastolic velocity (E) to obtain E/Ea.In all, 31 patients were imaged, with a mean LV ejection fraction of 47.7% +/- 19.9. There were significant correlations between Sa, Ea, and Aa by color and spectral TD at all sites (R = 0.92, P < .001 for Ea at basal lateral wall) and between spectral and color E/Ea (R = 0.85, P < .001). Sa, Ea, and Aa were significantly lower by color TD than by spectral TD (basal septal color Ea = 3.0 +/- 2.0 cm/s vs 5.6 +/- 2.5 cm/s for spectral Ea, P < .001). Consequently, E/Ea by color TD was significantly higher than by spectral TD (22.3 +/- 15.3 vs 13.6 +/- 7.8, P < .001).Although significant correlations exist, myocardial velocities measured using color TD significantly underestimate velocities by spectral TD. Consequently, E/Ea by color TD significantly overestimates E/Ea using spectral TD, which could lead to errors in assessment of LV diastolic function.