The present work was designed to study the histological changes of the rat’s circumvallate papilla following unilateral glossopharyngeal re-innervation. Unilateral re-innervation was achieved by transection of the 9th nerve and avulsion of its central segment on the right side and crushing that of the left side. The latter was thus allowed to regenerate and to re-innervate the papilla. On the first 2 post-operative weeks, the nerve bundles at the base of the papilla and the subgemmal nerve plexus showed signs of Wallerian degeneration and concomitant disappearance of taste buds. On the 3rd post-operative week, the papilla was invaded by regenerating nerves and the primordial taste buds started to appear. From the 4th week onwards, the number of regenerating taste buds on the left outer, left inner and right inner trench walls was not significantly different from the sham-operated controls. The only buds which failed to reappear were those of the upper two thirds of the right outer trench walls. The newly formed buds were smaller in size than those of the sham-operated controls with a relative diminution of 30% of the number of intragemmal cells per section of taste bu