An experimental resin composite loaded with newly designed spherical silica filler particles approximately 1.0μm and 0.1μm in diameter categorlized into duo-spherical type was developed. Several properties of the resin composite as mechanical properties, linear contraction, chemical degradation in an alkakine solution, color change during irradiation, SEM observation of filler particles and set resin, and polishability were examined.In addition, a clinical trial with the resin was performed. As a result, the experimental resin composite exhibited superior properties to the resin composites on the market and the esthetic characteristic was favorable in the clinical use with a good polishability.