In recent years, researchers have modified masses, stiffness or damping in structures to control their vibration instead of using traditional method which provides dissipation of earthquake-induced energy by the inelastic response of the structural members. Damage due to this yielding action is usually re-paired expensively or may be so serious that demol-ishing of building must be required. Here damping due to friction is considered as an energy dissipation method due to some advantages. Friction devices are generally capable of repeated cycles of dis-placement without loss of strength, stability or ener-gy dissipation. In addition, since they are fabricated from traditional materials. They require little maintenance; their use in seismic design and retrofit applications appears to be very promising. The new significant feature in performance-based earthquake engineering is the selection of seismic performance level for a given earthquake ground motion. In this article, the effectiveness of friction dampers on rein-forced concrete systems for immediate occupancy (IO) performance level is investigated considering the properties of the system and friction damper. A number of studies toward deriving a reasonable criterion for optimal design of frames with supple-mental dampers have been reported. Some of them have defined performance indexes which evaluate the performance of the system as the ratio of suitable parameters calculated for the damped brace frame to that for the unbraced frame. The others have used the acceptability limits for the structural response as performance criteria to select appropriate damper properties. In this study, the selection of brace stiffness and slip displacement level of friction damper for SDOF RC systems having different period and strength ratio is made considering the peak response values for IO level obtained from the comprehensive nonlinear time history analyses. The reason of selecting IO performance level is that the structure is only slight-ly damaged and the capacities of force resisting sys-tems have almost the same pre-earthquake ones in this level. Since both dynamic and inelastic response is modeled in nonlinear dynamic analysis permitted to be used for structures without any re-strictions, this procedure is used for the evaluation. Nonlinear time history analyses are performed using the force displacement relationships of bare RC sys-tem and friction damped brace. Q-hyst model is con-sidered for nonlinear dynamic response of RC sys-tem while elasto-plastic model is used to represent that of the damped brace here. Algorithm is devel-oped to perform 14400 nonlinear dynamic analyses formed by 9 different periods (0.1s-0.9s), 2 strength ratios for bare RC system and 4 brace stiffness, 5 slip displacement values for friction damper using 40 earthquake records. The earthquake records are taken at stations whose closest distances are less than 15 km to the fault. The average peak ground acceleration of 20 unscaled earthquakes for each soil profile is 0.35 g. Peak values of displacements and shear forces are stored. The limit value for average peak displace-ment is considered as the yielding displacement of bare RC system. The damper properties are selected from the cases providing this limitation with low base shear. As a conclusion, ductility and base shear demand are strongly dependent on the brace to the frame stiffness ratio, the device slip to the frame yield displacement ratio and the soil profile. Gener-ally base shear increases with the ratio of the brace stiffness to the frame stiffness and the device slip to the frame yield displacement. On the other hand, these conditions are opposite for the displacement demands. Although high brace stiffness ratio and slip displacement ratio warrant the displacement limitation, dissipated energy by friction damper de-creases and the behavior of the system shows simi-larity with braced one without any dissipation fea-ture. Higher brace stiffness causes greater decre-ment in displacement demand under the same slip load which can be obtained by using different brace stiffness and slip displacement ratio. For the period of bare RC system higher than 0.5s, required slip load level decreases for stiff soil profile while almost same load level is required for soft soil profile. In addition, lower slip load level is required to obtain performance objective for lower strength ratio of bare RC system. The results obtained are limited since only IO level is aimed for sites whose closest distances are less than 15 km.