The purpose of this study was to measure the compressive strength, flexural strength, microhardness, and surface roughness of three compomers (Compoglass, Dyract, and Hytac) and compare the values to the ones obtained for a resin-modified glass-ionomer cement (Vitremer) and a resin composite (Z100). All materials were handled according to the manufacturers' instructions. There was a significant difference (P < 0.01) among Vitremer, Hytac and Z100 composite with regard to yield strength. Vitremer values were lower than for Hytac, which were lower than for Z100. The yield strength values for Compoglass and Dyract were significantly lower than for Hytac and Z100 composite and significantly higher than for Vitremer (P < 0.01). There was no significant difference in the strain at yield among Vitremer, Hytac, and Z100, but their values were significantly higher than for Compoglass and Dyract (P < 0.01). The flexural strength data displayed a significant difference between Vitremer and Hytac (P < 0.05). Z100 was significantly stronger than the other products tested. The values of strain at break for Vitremer, Hytac, and Z100 were significantly lower than for Compoglass and Dyract (P < 0.01). The compressive strength results showed significantly higher values for Dyract, Compoglass, and Hytac than for Vitremer (P < 0.01). Z100 displayed higher values than the other products tested (P < 0.01). Hytac strength was significantly higher than for Dyract (P < 0.01). The microhardness of Compoglass and Dyract was not significantly different (P < 0.05). Hytac displayed microhardness values higher than for Vitremer, Compoglass, and Dyract (P < 0.01). However, all products tested showed values significantly lower than for Z100 (P < 0.01). The surface roughness values for Compoglass, Dyract, Hytac, and Z100 were not significantly different. Vitremer displayed a significantly higher value than Dyract, Hytac, and Z100 (P < 0.05).