Mirror movements are described in 3 members of a Negro family that is free from other neurologic abnormalities. The movements continued into adult life without change and persisted in 1 individual despite a flaccid right hemiplegia caused by a vascular accident. It is felt that the most likely explanation for mirror movements is distribution of the cortical motor neurons from each hemisphere to each cervtcal cord hand area, associated with incomplete crossing at the pyramidal decussation in the medulla.