STATEMENT OF PROBLEM: Failure of the bond between the acrylic resin and silicone based liner material is commonly encountered in clinical practice. PURPOSE: Examine effect of different treatment methods on the   tensile bond strength between a silicone –based liner and denture base before and after the thermocycling.  MATERIAL AND METHODS: 140 test samples were fabricated. The samples were divided into 14 groups (n=10), according to the treatments applied. To enhance the bonding capacity between these materials, acrylic resin surface was modified using acetone, methyl methacrylate(MMA),isobutylmethacrylate(IBMA), 2-hydroxyethylmethacrylate (2-HEMA), sandblasted with110 μm aluminum oxide particles (110 μmAL2O3) and combination between sandblasting and each of these chemical material individually while in the group 11 ,silicone based liner was immersed in IBMA but in the group 12, acrylic resin surface was modified using sandblasting and a silicone based liner was immersed in IBMA .in addition ,in the  group 13; silicone based liner was immersed in 2-HEMA  and Group 14, acrylic resin surface was modified using Sandblasting and silicone based liner was immersed in2-HEMA. Silicone based liner was processed between 2 PMMA blocks. In each group, five samples were thermo cycled in water bath (5-55˚C) 500 cycles before tensile testing, whereas the other five were directly tested without thermocycling using Instron testing machine with speed rate (1 mm/minute) to measure tensile bond strength by MPa. All data were statistically analyzed by One way ANOVA, Tukey post hoc test and Paired sample t-test. RESULTS: There was no statistically significant difference between all tested groups where (p=0.154) before thermocycling while after the thermocycling, there was a statistically significant difference between all tested groups where (p=0.001) but there was no a statistically significant difference between control and all other tested groups. Furthermore, there was no statistically significant difference between before and after thermocycling in each group except group 9. CONCLUSIONS: The different treatment methods had poor effect on the tensile bond strength. Thermocycling had poor effect on the tensile bond strength between a silicone –based liner and denture base except group9 (acrylic resin surface was modified using sandblasting followed by IBMA application).