In cats with upper spinal lesions disconnecting the dorsal column (DC) from the spinocervicolemniscal and ventral tract (VT) systems, single unit responses in the inferior colliculus could be evoked by DC and VT stimulation. Excitatory convergence and inhibitory interactions were observed between DC, VT, visual and auditory inputs both in the external and central subnuclei of the inferior colliculus.