Due to large individual differences of masticatory function, an inter-individual comparison between denture patients and complete dentate people would be insufficient. This cross-sectional study aimed to evaluate patients' masticatory performance (determined by Mixing Ability Index, MAI) and bite force (determined by maximum bite force, MBF) after removable partial denture (RPD) treatment by comparing those of the RPD replaced side with those of their own opposite dentulous side, and to evaluate influence of bite force on masticatory performance in different dentitions. Subjects included patients with unilateral distal extension RPDs (n=28). Apart from the RPD replaced area on one-side, all subjects had intact dentitions. Both masticatory parameters were evaluated separately on each chewing side. MAls and MBFs obtained from the RPD replaced side (0.65 +/- 0.50 and 220 +/- 155 N, mean +/- SD) were significantly lower than those from the dentulous side (1.06 +/- 0.64 and 450 +/- 268 N; Wilcoxon signed-ranks, P < 0.001). MBF significantly influenced MAI in both RPD replaced (Univariate linear regression; R2 = 0.17, P < -0.001) and dentulous sides (R2 = 0.51, P < 0.001). After RPD treatment, masticatory performance and bite force of RPD replaced side were lower than those of their own dentulous side. The influence of the bite force on masticatory performance in RPD replaced side was less significant than that in the dentulous side.