Suction performance of centrifugal pumps can in general be improved by the introduction of an inducer ahead of the main impeller. An inducer is substantially an axial-flow impeller having very steep head-capacity curve and low head coefficient characteristics near normal flow. An ordinary inducer may exert adverse effects on the pump due to the above characteristics. An inducer of special design was investigated with a view to overcoming faults encountered in an ordinary inducer by making full use of characteristics inherent in the axial-flow impeller in low flow range. With the new type of inducer and the addition of an orifice plate placed ahead of it, the values of NPSH at cavitation breakdown points decreased with decreasing flow rates and suction specific speed values of 7000 to 9000 (m³/min, m, rpm) were obtained at low flow rates.