Review of the anatomy of visceral afferent pathways. The peripheric nerve fibers of primary visceral afferents are both myelinated and unmyelinated. The myelinated fibers have caliber spectra encompassing categories from the largest to the smallest diameters.— The central connexions within the spinal cord of first order visceroafferent neurons are difficult to trace by anatomical means in consequence of the localization of both somatic and visceral primary sensory nerve cells in the spinal ganglia. An attempt is made to circumvent this difficulty by comparing degeneration patterns resulting from dorsal radicotomy in segments of comparable architecture having numerous (Th7–8) and relatively few (L3–4) visceral afferents. No useful difference could be observed in the substantia gelatinosa. Attention is called to the very massive degeneration encountered in the intermedio-medial nucleus in the level of Th7–8. Although the degeneration is still heavy in the same region in the level L3–4, however, it decreases sharply in the segments below. Considerable differences in degeneration patterns in Clarke's column after transection of dorsal roots subserving sensory innervation of the lower limb and of those from Th7–8 might suggest an entirely different — non proprioceptive (even perhaps visceroafferent) — function of the upper part of this nucleus. — In spite of its main involvement in cutaneous sensation the substantia gelatinosa from various reasons cannot be excluded from participation in visceral afferent transmission mechanisms. This problem is discussed briefly with respect to some new light- and electron microscopic information of its structures. — Ascending spinal and brainstem visceral pathways are discussed mainly in the light of recent information on the termination of antero-lateral tract fibers in brainstem regions other than the specific sensory nucleus of the thalamus. Several routes are suggested for visceral pain conduction, bypassing the nucleus ventralis postero-lateralis and reaching the frontoorbital cortex either directly over the dorsomedial thalamic nucleus or conveyed through the hypothalamus and the dorsomedial nucleus. — The role of the hypothalamus in transmission or integration of visceral afferent informations appears of having been underestimated. Evidence of mainly crossed ascending connexions between visceral receptors and the hypothalamus is discussed.