In this paper, two of our investigations of ultrasound image feedback control methods for a probe-holding robot are described. The first is an autonomous positioning system. The proposed algorithm enables the robot to autonomously search and detect the target organ, and obtain a clear ultrasound image. The second is a real-time visual servoing system that tracks the movement of the target organ. The proposed method requires only a normal 2-dimensional B-mode probe for 3-dimensional tracking. The results of testing in human tissue are also described.