The phase-Doppler technique (PDA) has become one of the most important instrumental methods in two-phase flow research in recent years because of its capability of simultaneously determining the diameter and velocity of spherical particles. However, the shortcomings of this technique with respect to volume Aux measurement have become increasingly apparent. fn order to study the performance of different PDA instruments, comparative flux measurements in two characteristic sprays using a patternator and three phase-Doppler systems were performed at the Institut Wr Thermische Stromungsmaschinen of the University of Karlsruhe (ITS) in cooperation with the Lehrstuhl fur Stromungsmechanik of the University of Erlangen-Nurnberg (LSTM) and DANTEC/invent Measurement Technology GmbH in Erlangen. The results of this study clearly indicate that especially in dense sprays, mass flux determination by the phase-Doppler technique is still critical. Further efforts to improve the reliability of the system and to identify the possible sources of errors are necessary. However, the dual-mode technique shows a significant improvement compared with the other instruments under investigation.