The recently developed dual-setting resin glass-ionomer cements are discussed, and the question of whether they are the true glass-ionomer cements is addressed. Their chemistry and properties are examined and compared with conventional glass-ionomer cements. Resin-modified glass-ionomer cements have the advantage of a long working time combined with a rapid set and higher early strength. They are also easily bonded to resins. They have the strength properties comparable to conventional glass-ionomer cements rather than composite resins, but they share with composite resins the disadvantage of containing free monomers and therefore may not be as biocompatible as conventional glass-ionomer cements.