PURPOSE: This study characterized the effect of water immersion on the strength of denture polymers. MATERIALS AND METHODS: Four denture-base polymers and four denture-reline polymers were tested for flexural strength at proportional limits (FSpl) at 24 hours and at monthly intervals. The equilibrium strength of each polymer was estimated. RESULTS: The denture polymers took from 24 hours to 4 months to reach their equilibrium strength. The equilibrium strengths of the denture polymers were significantly different. CONCLUSION: Water immersion affected the strength of most denture polymers. Different denture polymers behaved differently in response to water immersion.