Procedures for the seismic assessment of existing buildings are given in the 2007 Turkish Earthquake Code (TEC). Since Turkey is on active earthquake zone, performance evaluation of existing buildings is a need to minimize the possible casualties and economic losses. The seismic safety of a building depend on the structural configuration, on the layout of the columns and beams, seismic zone, soil type, material classification as well as on the number of stories. This paper deals with seismic assessment of existing reinforced concrete workshop buildings. In this study, the 17 workshop buildings having reinforced concrete frames are selected in order to investigate of seismic behavior of the buildings. Nonlinear flexural behaviors in frame members are defined to plastic hinges, where the plastic hinge length Lp is assumed as half of the section depth for beam and column elements. The plastic hinge properties are described as depending on element size, material properties, longitudinal and confinement reinforcement amount and detailing and axial load level on the element. Performance level of the buildings was determined by using the procedure for the performance evaluation via incremental pushover analysis with incremental equivalent seismic load method given in seismic code of Turkey, where the seismic performance evaluation is similar to that of FEMA 356. The performances of workshop buildings carried out for earthquake with 2% probability of being exceeded in 50 years and 10% probability of being exceeded in 50 years. Three-dimensional models of each of the buildings are developed and their analyses are performed by using SAP 2000 software program. These analyses are carried out for the buildings having the selected structural configuration by varying the number of story, the column sections, number of spans, concrete strength, steel yield strength, spacing of confinement reinforcements. The performance level of buildings were determined for two different material group in this study. The obtained results from analysis are evaluated in term of fundamental period, capacity curve, target displacement and building performance level for two different material group. The results show that concrete strength is one of the important parameter effecting the fundamental period in cracked cross section. However the effect on the un-cracked cross section period of concrete strength is less than the effect on the cracked cross section. The equivalent single degree of freedom approach is used to obtain target displacement according to 2007 TEC response spectrum. Target displacement requests in the direction of earthquake at the top of the buildings are obtained for two different material groups in the all buildings. The results show that the effect of material strength on target displacement value is quite little. The base shear force versus roof displacement curves of buildings are obtained by using plastic hinges at the both ends of the beams and columns. The ratio of base shear force to building weight (V/W) in “material group A” was found to be larger than “material group B” values. A large number of workshop buildings do not have enough seismic safety in “material group B”, since the most of them have been constructed without receiving any structural engineering attention. The buildings do also not have enough seismic safety in “material group A”, since the columns are generally replaced in one direciton in despite of regular design in the main structural system of the building.