Intraocular cyclophotocoagulation with endoscopic visualization, following lensectomy and anterior vitrectomy, was performed on 14 eyes of eight rhesus monkeys. Two eyes received lensectomy and vitrectomy without laser treatment. One eye of each animal was studied one to eight months postoperatively, while the contralateral eyes were enucleated for study immediately after surgery. Histopathologic changes in the treated ciliary processes immediately after therapy included variable degrees of disruption in the epithelial layers and bleeding, while the late changes ranged from partial disruption of the epithelium and intrastromal pigment clumping to replacement of the processes by a fibrotic mass. The degree of these structural changes correlated reasonably well with the level of laser energy used and especially with the immediate, visible tissue alteration. These data may be useful in the development of clinical protocol for intraocular cyclophotocoagulation.