This paper presents the design and construction of a 12-DoF biped walking robot. The kinematics of electrically actuated 6-DoF legs is similar to that of human legs with three DoF at the hip, one at the knee and two at the ankle joints. The mechanical design of the robot was based on dynamical simulations realized in a modular PC environment. Two communicating software were used in order to solve the forward dynamics of the system and to design walking controllers. Forward, backward and lateral walking as well as stair climbing behaviors with up to 6 km/h forward walking speeds have been simulated in order to determine the nominal power rates required at joints. Hip joints are actuated by DC motors coupled to harmonic reducers situated both in joint axes. The actuators driving the knee and ankle joints are situated higher than the respective joint axes and the rotational output motion of DC motors are transmitted to the joints through linear ball-screw mechanisms. Spherical joints are used within the transmission of spatial motion required for the 2-DoF at ankle joints. All joints consist of absolute encoders and 6-axes force/torque transducers are mounted at the ankle joints. The robot is controlled through an embedded industrial PC running real-time operating system. All electronic control hardware including the motor drivers and sensors communicate through CAN bus. The robot's mass without batteries is 55 kg and its height is 142 cm.