The incorporation of prepolymerized-filler particles in hybrid resin composite systems may result in a reduction of mechanical properties. SUMMARYThis study compared the properties of newer hybrid resin composites with prepolymerizedfiller particles to traditional hybrids and a microfill composite. The following properties were examined per composite: diametral tensile strength, flexural strength/modulus, Knoop microhardness and polymerization shrinkage. Physical properties were determined for each composite group (n=8), showing significant differences between groups per property (p<0.001). In general, the traditional hybrid composites (Z250, Esthet-X) had higher strength, composites containing pre-polymerized fillers (Gradia Direct Posterior, Premise) performed more moderately and the microfill composite (Durafill VS) had lower strength. Premise and Durafill VS had the lowest polymerization shrinkage.