A Doppler gate is automatically positioned in spectral Doppler ultrasound imaging. Samples acquired for multiple PW Doppler gates are used for B-mode and/or F-mode detection over time without interleaving transmissions for the PW Doppler. The B-mode and/or F-mode information are used to track gate placement. Alternatively or additionally, characteristics spectra from different gate locations are used to select a gate location. Either tracking may be used to change the locations sampled and/or beam characteristics, such as centering the locations and beam focus on the selected gate location.