Behavioral extraction from circuit description is a useful technique for logic design verification. We have proposed a technique of extraction from combinational circuits and developed a prototype system. To use this system practically, it is necessary to deal with sequential circuits. In this paper, we will present a new technique to extract behavioral descriptions from synchronous sequential circuits which include some flip-flops. Flip-flops are classified to two types. The one is a part of control registers. The other is a part of data registers. Behavior of the circuit with control registers is described by the state transition. Behavior of the circuit with data registers is described by the movement of data among registers. There are many circuits, as micro processors, which realize a function after some times of state transitions occurred. In such circuits, it is more important to abstract the function than to extract each state transition. We have progressed our system to extract such behaviors.