Objective: The purposes of this study are to study the effect of crown venting and type of cement on retention of cemented-retained implant prosthesis.Materials and Methods: Eight Spline Calcitek implants were mounted in acrylic resin blocks in pair. A titanium abutment was placed on each implant and torqued at 28.2 Ncm. The crowns were casted with Nikel-Cromium alloy in pair and tested with three different cements. The three cements were: HY-Bond(R) (Zinc Phosphate Cement), IRM(R) (Reinforced Zinc-oxide eugenol) and Resiment(R) (Resin cement). After cementation, implant-abutment-casting assemblies were thermocycled in water bath at 5 ํC, room temperature and 55 ํC for 30 second dwell time per bath and 1500 cycles. Cyclic loading was applied with Instron Dynamic UTM with peak load between 125 and 290 N at speed of 5 Hz. for 100,002 cycles. Samples were subjected to a pull-out test using Instron UTM at crosshead speed of 5 mm./min. The load required to de-cement each coping was recorded and mean values for each group calculated. The crowns were vented and tested with the same method with different cements mentioned. Mean and standard deviations of loads at failure were analyzed using Mann-Whitney U Test. Statistical significant was set at p[is less than or equal to] 0.05. Result: The mean values (+-SD) of loads in Newtons at failure (n=10) for the various cements were as follows: In non-vented crowns of IRM(R), Resiment(R) and HY-Bond(R) were 254.44 +- 63.33, 233.50 +- 70.72 and 191.22 +- 64.24, respectively. In vented crowns of Resiment(R), IRM(R) and HY-Bond(R) were 312.72 +- 85.78, 236.30 +- 77.16 and 152.67 +- 54.98, respectively. Statistical test revealed no significant difference between vented and non-vented crowns for HY-Bond(R) and IRM(R) except for Resiment(R). In non-vented crowns there were no significant differences among any cement. In vented crowns there were significant difference between HY-Bond(R) and IRM(R) and between HY-Bond(R) and Resiment(R), but no significant difference between IRM(R) and Resiment(R). Conclusion: Venting has effect on retention when using Resiment(R), but not with HY-Bond(R) and IRM(R) at p[is less than or equal to] 0.05. In non-vented crowns, type of cement has no effect on retention at p[is less than or equal] 0.05. In vented crowns, type of cement has effect on retention at p[is less than or equal] 0.05.