The present study was conducted to evaluate the adhesion potential of bacterial colonies on thermoplastic resin relining material (Versacryl) and compared it with the conventional heat-cured polymethyl methacrylate acrylic denture base material.Ten completely edentulous diabetic patients with no history of denture experience had participated in this study. Patients in this study were precisely selected and thoroughly examined in an attempt to reduce human variables and eliminate any factor or habit that might adversely affect the results of study. All selected patients were re-habilitated by mucosa supported complete dentures. Standard clinical and laboratory techniques were followed for denture construction. According to the utilized relining material, the patients were randomly divided into two groups as the patients were tested as own control group: -Group 1: Patients in this group were rehabilitated with conventional heat-cured polymethyl methacrylate acrylic denture base polymerized following the water bath technique.Group II: Patients` dentures in the previous group were relined with thermoplastic resin (Versacryl).The effect of each of the previously mentioned denture relining materials on bacterial counts was assessed by sampling the multiple surfaces of the patient`s oral cavity and denture following the swab technique. The colony forming units (CFU) of organismswere visually counted,tabulated and prepared for statistical analysis. Samples were collected at a month after denture insertion for each week time interval. Swabs were taken from the oral cavity and from the denture before and after delivery of the denture by intervals of one week between each swab by total time one month for all swabs, four swabs before relining and other four swabs after relining. These swabs were implanted in blood agar plates which were put inside incubator 37co for 24 hours then the count was taken for the bacterial colonies per ml in terms of (CFU\ML).Data were tabulated and statistically analyzed.The results showed that Versacryl thermoplastic resin materials have higher affinity for bacterial colonization.Conclusions: 1.Diabetic complete denture wearers may have higher bacterial growth than normal subjects.2.Both methyl-methacrylate and thermoplastic resin materials may induce bacterial colonization. 3.Versacryl thermoplastic resin materials may have higher affinity for bacterial colonization.