The article provides the results of morpho-functional studies of groups of associative neurons considered as premotor interneurons (PI) of the spinal cord. The issues of their topography are covered, the structural and functional diversity of this type of interneurons, the orientation of the processes and their neurochemical characteristics are analyzed. It is shown that the differences between PIs are genetically determined. The results of the study of the activity of glutamate, GABA, AChE, HAT, CAB, NOS and NADP-diaphorase in this group of neurons are also presented and confirmed by own research. Contradictory data on the modular structure of the spinal cord are given. The data analyzed in the review allow the authors to suggest the existence of a complex cluster of premotor interneurons that affect motor neurons and autonomic (vegetative) neurons that are the part of the spinal cord nuclei.