The purposes of this experiment were to determine if resin-modified glass-ionomer cements are less sensitive to moisture than are conventional glass-ionomer cements, to investigate the effects of barrier coatings, and to study the effects of different setting environments. Discoid specimens of a variety of resin-modified glass-ionomer materials and a conventional glass-ionomer cement control were stored in different environments and were protected with different barrier coatings. The diametral tensile strengths of the specimens were determined and analyzed with three-way analysis of variance. Resin-modified glass-ionomer cements are less sensitive to moisture than is the conventional glass-ionomer cement control. Drier environments produced stronger resin-modified glass-ionomer strength, and the individual materials differed in strength.