Akinesia, the core symptom of the parkinsonism, which is the term having been used routinely in daily practice of neurology in describing the specific motor disturbance in parkinsonian patients, is not well defined in sense of its generating mechanism. The author tried to analyze this concept from physiological and pharmacological standpoint and classified into three subgroups, i.e. slowness of movement, poverty of movement and difficulty in initiating repetitive movement. These three groups are interpreted as due to deficiency either of DA or of NE, the former being related to the slowness of movement and the poverty of movement and the latter to the freezing symptoms in the later stage of illness. Parkinson's disease now should better be understood as the result of deficiency of several catecholamine metabolites due to chains of enzymic error, and not only of DA.