Purpose: This study was undertaken to characterize the shear bond strength established between four denture base polymers and four denture reline polymers. Materials and Methods: Cylindric columns of denture reline polymers were bonded to columns of denture base polymers. Specimens were immersed in water for 4 months and then thermocycled. The strength at which the bond failed under shear stress was recorded. Results: Significant differences in bond strength existed among the specimens because of the denture base polymer variable, the denture reline polymer variable, and their interaction (P < .05). A light-activated denture base polymer (Triad) bonded adequately with a light-activated reline polymer (Triad) but less well with the other reline polymers tested. The bond strength established between some denture base polymers and a different light-activated reline polymer (Rebaron LC) was relatively low. Conclusion: The type of denture base polymer and denture reline polymer affected the shear bond strength between them. Int J Prosthodont 2001;14:271–275.