Intrathecal implants of adrenal medullary chromaffin cells relieve chronic pain by secreting catecholamines, opioids and other neuroactive substances. Recently, macrocapsules with hollow fibers were employed to isolate immunologically xenogeneic chromaffin cells, but the poor viability in vivo of the encapsulated chromaffin cells limited the usefulness of this method. In this study, we used microencapsulation technology to increase the viability of chromaffin cells. Bovine adrenal chromaffin cells were microencapsulated with alginate and poly-L-lysine and implanted intrathecally in a rat using the neuropathic pain model. Intrathecal implants of microencapsulated cells relieved cold allodynia, which is the most prominent symptom of the neuropathic pain model in a rat. Furthermore, the microencapsulated chromaffin cells were morphologically normal and retained their functionality. These findings suggest that the intrathecal implant of microencapsulated chromaffin cells might be a useful method for treating chronic pain.