Spinal microglia have been implicated in the pathogenesis of neuropathic pain after peripheral nerve injury concomitant with diseases such as diabetes and cancer. To reveal the etiological roles of microglia in behavioral pain hypersensitivity or neuronal excitability, technical approaches have been used. Here, we describe a technique for intrathecal transfer of cultured microglial cells through a catheter surgically implanted into the spinal subarachnoid space.