Purpose: The posterior palatal seal is a very important determinant in retention of the complete denture. It can be subjected to distortion during the relining procedures. The purpose of this study was to evaluate the dimensional accuracy of various denture relining materials on the maxillary posterior palatal seal area. Materials and Methods: A stainless steel cast was constructed from an ideal maxillary edentulous cast. Fifty identical complete dentures were fabricated on 50 definitive casts made from the original metal cast. Five relining methods and materials were evaluated during this study, in regards to posterior palatal seal distortion: (I) laboratory conventional heat–polymerizing (Lucitone), (II) conventional auto polymerizing resin : DPI–RR, (III) chair side relining material (Monosill) . The dimensional change occurred in the region of posterior palatal seal areas were determined by placing a low–viscosity silicone impression material between the metal cast and the tissue surface of the relined dentures. The thickness of the silicone was measured at five predetermined points, under a measuring microscope. Statistical analysis was performed using descriptive statistics, One way Anova test, Tukey’s HSD test. Results: The gap at the posterior palatal seal area ranged from 247 to 773 μm, when measured at the five predetermined points. Point E exhibited the smallest mean gap in group III and least in point C and Group I revealed the largest mean discrepancy. The different relining methods and materials presented statistically significant differences (p < 0.0001). Conclusion: The chairside autopolymerizing relining material exhibited smaller gap recordings than the rest of the tested complete denture relining materials at posterior palatal seal area.