Statement of Problem:  A removable partial denture (RPD) is a common treatment modality for restoration of partially edentulous ridges. How ever this type of treatment may produce serious periodontal problems for remaining teeth.Purpose: The aim of this study was to determine the effects of RPDs with RPI design on the periodontal indices of abutment and non abutment teeth.Materials and Method: For this interventional and prospective study, 22 patients (30-68 years old; mean age of 48 years) were selected. All patiets has Kennedy class I partial edentulous areas and were supposed to use removable partial dentures. Forty eight abutment and 48 non abutment teeth were assigned for this study .Clinical parameters including clinical probing depth (CPD), clinical attachment level (CAL), keratinized gingival width (KG), gingival index (GI) were measured in abutment and non-abutment teeth at baseline,1,4 and 12 months after delivery of  RPDs. Data were analyzed using wilcoxon test.Results: All clinical indices with the exception of gingival index, at the time of baseline to 12 months, showed significant differences between abutment and non-abutment teeth ( p<0.001). Significant differences were also noted for all indices between abutment and non-abutment teeth after 12 months.Conclusion: The results of this study indicated that removable partial denture with RPI design plays an important role in producing and intensifying the periodontal diseases in both abutment and non abutment teeth. It seems that this effect is due to the accumulation of more bacterial plaque. So, use of appropriate design and recommendation of good oral hygiene may decrease the severity of side effects.Key Words: Removable partial denture, Abutment and non-abutment teeth, Periodontal indices