Dissection, light and electron microscopy combined with degeneration induced by intracranial nerve lesions and superficial nerve transection were used to trace the sources of sensory fibres of the inferior conjunctiva of cynomolgus monkeys. Most nerves destined for the inferior conjunctiva were branches of the lacrimal nerve and entered the inferior eyelid laterally. Following unilateral ophthalmic neurotomy in three monkeys and combined ophthalmic/maxillary neurotomy in one monkey, substantial and regular degenerative changes were observed in the nerves and nerve-fibre bundles of the inferior conjunctiva. Following intracranial lesions of the maxillary nerve and of the infra-orbital nerve at its facial hiatus, conjunctival nerves showing induced changes were infrequent (four animals) or absent animal). The results indicate that the inferior conjunctiva is innervated mainly by the ophthalmic nerve contrary to the popular notion that it is innervated mainly or wholly by the infra-orbital branch of the maxillary nerve.