Objective: Restorative materials that possess antibacterial properties are considered advantageous. The aim of this study was to test the antibacterial properties of packable resin composite materials using a direct contact test (DCT) and an agar diffusion test (ADT). Methods and materials: Quadruple samples of SureFil, Alert, P-60, Synergy Compact, Pyramid, and Solitair were placed on the sidewalls of wells in a 96-microtiter plate, and polymerized. A suspension of 10-µL growth medium containing ca. 1 × 10⁶ viable mutans streptococci cells were placed on the surface of each sample for 1 hour at 37°C. Fresh medium was then added to each well, and the microtiter plates were placed in a temperature-controlled spectrophotometer which also served as an incubator. Bacterial growth was followed by recording the changes in optical density every 30 minutes for 16 hours. The ADT was performed by placing samples in punched wells of inoculated agar plates, and measurement of the inhibition zone was performed after 72 hours. Results: In both tests, none of the materials inhibited growth of S mutans. In the DCT, three materials enhanced bacterial growth. Composite samples, aged in phosphate buffered saline for 7 and 30 days, showed no differences when on tested material and controls. Conclusions: Packable composite materials revealed no antibacterial properties. Furthermore, freshly polymerized composites supported bacterial growth.