We analyzed morphological and histoenzymologic changes in spinal cord ganglionic neurons of mongrel dogs caused by epidural infusion of isobaric 2% lidocaine. Lidocaine produced no pathological structural and metabolic alterations in the nervous tissue. Both epidural infusion of 0.9% NaCl and lidocaine produced some morphofunctional rearrangements in spinal ganglionic neurons. These alterations were within the limits of physiological norm and probably attested to functional response of the examined nerve tissue structures to epidural infusion.