To measure and compare the fracture toughness of a multi-purpose resin composite, four light-cured glass ionomers, one light-cured resin ionomer, and two silver-containing glass ionomers.Ten specimens were fabricated for each of the eight materials: Herculite XRV, Fuji II LC, Photac-Fil, Vitrebond, Photac-Bond, VariGlass VLC, Ketac-Silver, and Miracle Mix. All materials were handled according to manufacturers' instructions during specimen fabrication, stored in 100% humidity for 2 weeks, and tested wet in a universal testing machine.The mean fracture toughness values (MPa . m(0.5) + or - S.D.) were: Herculite XRV = 1.17 + or - 0.09, Fuji II LC = 1.37 + or - 0.10, Photac-Fil = 1.27 + or - 0.08, VariGlass = 0.90 + or - 0.07, Vitrebond = 0.88 = or - 0.06, Photac-Bond = 1.09 + or - 0.09, Ketac-Silver = 0.51 + or - 0.08, and Miracle Mix = 0.30 + or - 0.07. There was a significant difference in the means (ANOVA P<0.0001). Fuji II LC and Photac-Fil were significantly tougher than any of the other materials (Tukey's HSD test P<0.01).