OBJECTIVE To evaluate and compare diametral tensile strength (DTS), compressive strength (CS) and flexural strength (FS) of a hybrid and a microfill resin composite restorative material polymerized by an argon laser for 10 seconds (AL10) and 20 seconds (AL20) vs. a conventional visible light for 40 seconds (VL40). METHODS Five specimens of resin composite, Herculite XRV, shade A-2 and Durafill VS, shade B-2, were made for each set of physical properties tested, for a total of 18 groups and 90 specimens. ANSI/ADA Specification #27 for direct filling resins was used as the protocol for specimen preparation and physical properties testing. An argon laser at approximately 285 mW, 6 mm beam size, power density of approximately 1,000 mW/cm2, and a conventional visible light at approximately 470 mW, 13 mm beam size, power density of approximately 354 mW/cm2, were used to polymerize the composite. Samples were stored in water in light-proof containers at 37 degrees C for at least 7 days and then tested on a Zwick universal testing machine. Mean DTS, CS or FS (MPa) values were calculated for each group. RESULTS Herculite XRV's physical properties were not significantly affected by light source or exposure time. Light source or exposure time had no significant effect on DTS for Durafill VS. Significantly lower FS was found for Durafill VS, when cured for 10 seconds with the argon laser compared to 20 seconds with the laser or 40 seconds with the conventional light. In addition, significantly lower CS was found for the Durafill VS when polymerized with the laser at 10 seconds compared to the conventional light at 40 seconds.