Purpose analysis of bond strength of various denture relining materials to recently introduced thermoplastic monomer free semi rigid microcrystalline polymer and heat cured denture base materials.Materials and methods: designed with cylindrical -shaped silicon patterns with dimensions 20 mm in length and 8mm in diameter. Samples branched into four groups(20 samples for each group):GI: heat cured acrylic resin samples with hard relining material, GII: heat cured acrylic resin samples with soft relining material. GIII: thermoplastic monomer free semi-rigid microcrystalline polymer (karadent) samples with hard relining material, GIV: thermoplastic monomer free semirigid microcrystalline polymer samples with soft relining material .Tensile and shear bond strength of hard & soft reliner to the two denture base materials examined by Instron Universal Testing Machine . Multiple group comparisons was assisted by one-way ANOVA test followed by T-test for pair wise comparisons to estimate any significant differences between groups. The tests deemed significant when p ≤ 0.05 and highly significant when p ≤ 0.001.Results: Highly significant differences for both tensile and shear bond strength mean values was found between groups regarding the mean applied loads, P-value ≤ 0.001. The t-test for comparison showed a extremely significant variance in the mean tensile & shear bond strength between groups. Hard relining material showed greater mean values of both shear and tensile bond strength regarding the heat cured denture base material (GI) followed by karadent one (GIII) . The lowest mean values was found in soft relining material, specially that with karadent denture base material ( GIV) for both shear and tensile bond strength.Conclusion: supporting on the results of this research, it might be terminated that newly introduced thermoplastic monomer free semi rigid microcrystalline polymer successfully accept relining specially with hard relining material .It overcomes the main problems of thermoplastic resins that can't accept relining (3560)