Aim of the study: The aim of this in-vitro study was to evaluate the effect of artificial aging (storage in artificial saliva and thermocycling) on the microleakage of new CAD/CAM provisional crown system VITA CAD-Temp in comparison with currently used bis-acrylic Protemp 4 luted with different non eugenol provisional cements. Materials and Methods: Forty freshly extracted intact human lower first molars with completely formed roots were collected. each tooth was vertically embedded in an acrylic block. Teeth were machine milled using a lath to achieve a standardized coronal preparation with 1 mm shoulder finishing line and 10° axial taper with the side wall length 4.5 mm with flat occlusal reduction, A groove was then cut in the occlusal surface along central fissure mesiodistally. The forty prepared teeth were divided into two groups of twenty teeth each according to the tested provisional crown system: GroupI: Machinable provisional system. (VITA CAD-Temp). GroupII: Two pastes bis-acrylic composite system for provisional prosthetic restoration ( Protemp 4). Each group was further sub divided into two subgroup according to the type of provisional cement used: Subgroup a: Samples luted with Zinc oxide free eugenol provisional cement. (TempBond NE ). Subgroup b: Samples luted with Resin- based provisional cement.(TempBond . Clear). Each subgroup was divided into two divisions: Division I: luted samples not subjected to artificial aging. (Control group) Division II: luted samples subjected to artificial Aging.( Test group). Microleakage was assessed by dye penetration distance in (mm) and scoring system (Lishman dye) method and evaluated using digital microscope with and without artificial aging. Results: The results showed that there was statistical significant difference between VITA CAD-temp provisional crown system and protemp 4 crown system with lower leakage values for protemp 4 crown system and also there was statistical significant difference between TempBond NE provisional cement and Temp Bond Clear provisional cement with lower leakage values for Temp Bond Clear provisional cement. Conclusion: VITA CAD-temp provisional crown system recorded higher leakage values than protemp 4 crown system with and without artificially aging. Temp Bond NE provisional cement recorded higher leakage values than TempBond Clear provisional cement. Artificial aging affected the leakage value of both provisional crown systems and provisional cements. Measurement of dye penetration depth in (mm) was more accurate than scoring system measurement.