A study is made on the behavior of shear wall systems made from large precast panels. Three commonly used wall arrangements are studied. The loading consists of monotonically increasing lateral uniform load. Realistic vertical joint and connecting lintel characteristics are incorporated into the mathematical model. A step by step calculation technique is used to study the vertical joint and lintel behavior and its effect on the overall stiffness degradation of the system as load increases. The effect of flexible foundation on the overall behavior is also studied.