OBJECTIVE To measure the water sorption and solubility of different resin-based restorative dental materials. METHODS Eight commercial restorative materials were selected: two resin composites (Z100 and Prodigy), four polyacid-modified resin composites (Compoglass, Compoglass F, Dyract and Dyract AP), and two light-cured glass ionomers (Vitremer and Fuji II LC). Five disc specimens were prepared of each material, following the manufacturer's instructions, and were grounded wet with silicon carbide paper. Water sorption and solubility of the different materials were calculated by means of weighting the samples before and after water immersion and desiccation. Data were analyzed by one-way ANOVA and Student-Newman-Keuls tests (P<0.05). RESULTS Compoglass and Compoglass F showed the lowest values of water sorption and solubility, while Vitremer and Fuji II LC displayed the highest values. Solubility values of Prodigy, Z100, Dyract and Dyract AP did not show significant differences among them, while their water sorption values attained some differences and were lower for Prodigy followed by Dyract and Z100. CONCLUSIONS The attained water sorption and solubility values are mainly influenced by the generic type of material and variations occurring between materials of the same type may result from differences in resin matrix compositions.