The purpose of this study was to determine the effect of intracanal medicaments on the sealing ability of commonly used provisional filling materials. Ninety extracted, unrestored human molars were prepared. The contents of the pulp chamber were removed, and distal and mesial root canal systems were cleansed to a size 25 file. Group A receive d a cotton pellet with no medication, group B a cotton pellet with Cresatin, and group C a cotton pellet with 2% iodine potassium iodide (IKI). The prepared teeth from each category were divided into three subgroups of 10 to receive Cavit, IRM, or TERM. After the fillings were placed, the teeth were thermocycled, stained, and sectioned longitudinally. The average dye penetration was greater in the medicated groups (B and C) than in the control group (A) for each provisional material tested. Statistical analysis revealed that sealing ability of all three filling materials was significantly affected by Cresatin and 2% IKI.