Statement of problem: Color stability is an important property of denture base acrylic resin. Color changes indicate aging or damaged dental materials. However, little information is available on the influence of denture cleansers on the color stability of acrylic resins. Purpose: The purpose of this study was to determine the influence of denture cleansers on the color stability of 3 different types of acrylic resin. Material and Methods: One heat-polymerized (HP) acrylic denture base resin (Acron), 1 autopolymerized (AP) hard direct reline acrylic resin (Denture Liner), and 1 visible-light-polymerized (VLP) hard direct reline acrylic resin (Tokuso Lite-Rebase) were evaluated. Five specimens of each material, 10 × 10 × 2 mm, were immersed in 1 of 9 commercial denture cleanser solutions or distilled water (control). Color changes were measured with a colorimeter and evaluated using the CIE L*a*b* colorimetric system. Data were analyzed using 1-way and 3-way ANOVA and the Student-Newman-Keuls test (α=.05). Results: Significant differences (P<.05) were found among the acrylic resins and denture cleansers in terms of color change (ΔE) produced after 365 days. The ΔE values of all denture base acrylic resins increased with time. The ΔE of the AP acrylic resin was larger than that of the other acrylic resins. The least discoloration was found with ZTC denture cleanser (acid type). The influence of alkaline peroxide-type denture cleanser (Steradent) on the color stability of HP acrylic resin and AP acrylic resin was significantly greater (P<.05) than that of the other cleansers. Conclusions: These results suggest that the color stability of denture base acrylic resins is influenced by polymerization type and the type of denture cleanser used. (J Prosthet Dent 2009;101:205-213).