1,1,1-Tris[4-(2'-hydroxy-3'-methacryloyloxypropoxy)phenyl]ethane (THMPE) and tris[4-(2'-hydroxy-3'-methacryloyloxypropoxy)phenyl]methane (THMPM) were synthesized and evaluated as base monomers in a dental composite system. The photopolymerization reactivity of the trifunctional methacrylates was similar to that of conventional 2,2-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl]propane (bis-GMA). Of the three monomers (THMPE, THMPM, and bis-GMA), THMPE has the greatest molecular volume, and its composite showed the lowest photopolymerization shrinkage of the composites derived from the three monomers. The water-solubility values for the light-activated composite resins formulated with THMPE and THMPM were much lower than that for a control bis-GMA composite. The trimethacrylates were not leached out into water from their corresponding photo-cured composites whereas the difunctional bis-GMA was eluted from its composite. The water sorption and flexural strength of the composite resins based on THMPE and THMPM were comparable to those of the bis-GMA composite. THMPE is promising for application as a photocurable dental monomer because of its good polymerization reactivity along with relatively low curing shrinkage and water-solubility of its photo-cured composite.