Combining color and spectral data, Doppler signal provides physiologic information about arterial and venous hemodynamics and anatomic information about vessel walls and diameter. Adequate sampling of Doppler signal is required to avoid pitfalls in interpreting spectral changes or color images. The level of information contained in spectral waveforms is high, compared with color display in terms of velocity profile alterations, as in stenoses, and cyclic changes of systolo-diastolic velocities. Therefore, integration of information from both types of Doppler signal representations is mandatory in clinical practice.