An autoradiographic study of the corticospinal projections from different parts of the cat sensorimotor cortex produced the following findings. The lateral part of area 4 projects contralaterally to the lateral intermediate zone of the cervical enlargement only. The intermediate part of area 4 projects throughout the spinal cord, contralaterally to the lateral part of the intermediate zone and bilaterally to its ventromedial part. The lateral and medial part of area 3 project contralaterally to the cervical and lumbosacral dorsal horn (including laminae I and II), respectively.