The object of this paper is to investigate the effects of cavitation on the discharge coefficientof sharp-edged, orifice plates with reference to various degrees of cavitation asdefined by a cavitation number. The experimental data described in this paper substantiatethe fact that cavitation can exist to a minimum cavitation number of 0.2without introducing errors in the orifice discharge coefficient in excess of the normalexpected accuracy. In addition to this, it was found that the use of air-inhalation tosuppress the vibration and noise from the cavitation had no effect on the dischargecoefficient.