Statement of the Problem: Adequate COMPRESSIVE STRENGTH is an important characteristic for an ideal liner. Purpose: This study aimed to assess the COMPRESSIVE STRENGTH of several commonly used liners. Materials and Method: This in vitro, experimental study evaluated 120 samples fabricated of Dycal, Calcimol LC, Vitrebond, Activa Bioactive, and TheraCal LC (n=24) liners accord-ing to the manufacturers’ instructions. The samples were fabricated using a cylindrical stain-less steel mold with 6± 0. 1 mm height and 4± 0. 1 mm internal diameter. Half of the samples in each group (n=12) underwent COMPRESSIVE STRENGTH test immediately after completion of their primary setting while the other half (n=12) underwent COMPRESSIVE STRENGTH test after 24 h. During this period, the samples were immersed in deionized water (grade 3) and incu-bated at 37± 1° C and 100% humidity for 24 h. The COMPRESSIVE STRENGTH was measured us-ing a universal testing machine. Data were analyzed using two-way ANOVA followed by Tukey’ s post-hoc test. Results: The COMPRESSIVE STRENGTH of the five liners was significantly different (p< 0. 05). Calcimol LC showed maximum COMPRESSIVE STRENGTH both immediately after setting and after 24 h. The COMPRESSIVE STRENGTH at 24 h was significantly higher than the primary com-pressive STRENGTH in all groups (p< 0. 05). Conclusion: Within the limitations of this study, it seems that Calcimol LC, Activa Bioac-tive Liner, and TheraCal LC have adequate COMPRESSIVE STRENGTH and can be used alone to provide adequate support for the restorative materials.