Microorganisms captured under restorations or penetrating via marginal gaps cause secondary caries and pulpal pathology. Dental cements that possess antibacterial properties can serve as a secondary line of defense and contribute to prolonged survival of cemented restorations. The purpose of the present study was to evaluate the antibacterial properties of three cements for fixed cementation using the direct contact test (DCT). Octet samples of Harvard cement (Richter and Hofman), Duralon (ESPE) and Ketac-Cem Radiopaque (ESPE) were placed on the sidewalls of wells of a 96 microtiter plate. Samples were left to set according to manufacturer’s instructions and ca.106 freshly grown S. mutans cells were placed on the surface of each sample for 1 h at 37ºC. Fresh media was added and bacterial growth was followed by temperature controlled spectrophotometer. The DCT was repeated on cements aged in phosphate buffer saline for 24 h, 1 week and 3 months. The antibacterial activity of Duralon and Harvard cement lasted for 3 months.