The results of the study of primary morphological manifestation of neuroleukemia (MMN) by mice with transplanting leukemia strains L 1210, P-388, L 5178Y, and are presented. It is determined that the MMN development degree depends on the leukemia cells dissemination amplitude after their transplantation and, in particular, on the degree of the bone-marrow affection, from which the leukemia cells grow into the dura mater encephali and epidural fat of the vertebral canal from the side of skull bones and vertebral canal. The analogous dependence is assumed to be present in a man and, therefore, there appears the possibility of using it for the neuroleukemia development frequency prognosing.