The test specimens were processed by autopolymerizing poly(methylmethacrylate) (PMMA), and their surfaces were untreated, polished in conventional manner with rag wheel, or coated with light-curing resin. The residual methylmethacrylate (MMA) content and its release into water from die specimens were measured with high-performance liquid chromatography. The lightcuring resin coating reduced most effectively the release of residual MMA into water during 2-day storage, but conventional polishing of the PMMA surface had similar effect when the mean values of groups were tested by means of one-way ANOVA (p<0.001). The residual MMA content was lowest in the test specimens coated with lightcuring resin, whereas only slight difference was seen when the untreated and polished test specimens were compared. This study suggests that not only light-curing resin coating but also the conventional polishing of the denture PMMA reduces residual MMA release into water in vitro.