We present new ideas about motor control in the human central nervous system and about pathophysiological mechanisms of Parkinson's disease, and we describe the Posturo-Locomotion-Manual (PLM) method, which is a new technique utilizing optoelectronic camera recording for objective, fully quantitative, and standardized assessment of human motor performance. In the PLM test, recordings of body movements are made during a simple motor task, where the subject repeatedly moves a small object from its starting position on the floor to a shelf located at chin height a few steps forward. The duration of the postural (raising up), locomotor and the goal-directed manual phase of the forward directed body movement is automatically calculated by a small computer as well as the degree of coordination (simultaneity) of these phases. The technique has high resolution and has been used for clinical assessment of motor performance, drug testing, and so on, in neurological and geriatric practice.