The clinicopathological features of 37 patients with invasive melanoma of the conjunctiva have been studied. Prognosis was closely related to the subsite and size of the primary tumour. Twenty of 21 patients with small localized bulbar neoplasms (95%) and four of six patients with diffuse bulbar melanomas (67%) have survived with no evidence of secondary spread. By contrast, only one of six patients with neoplasms involving the fornix (17%) and two of four (50%) with caruncular melanomas have survived. Metastatic spread was very uncommon in patients with melanomas less than 1.5 mm in maximum thickness, but the outcome of the disease in patients with tumours greater than 1.5 mm was not always bad. Treatment by local excision biopsy was followed by a high rate of conjunctival recurrence (59%). Exenteration of the affected eye guarded against the development of further orbital disease, but was not infrequently followed by the appearance of metastases. Many (62%) of the tumours appeared to have arisen in a pre-existing melanotic lesion or pigmented naevus of long-standing. Histologically, the tumours could be divided into those with an adjacent intra-epithelial component, manifest as atypical melanocytic hyperplasia in the conjunctival epithelium adjacent to the invasive melanoma, and those without (nodular melanoma). However, clear separation of the former group into the subtypes described for cutaneous melanomas proved impossible. Prognosis was not related to the type of melanoma, mitotic rate, cell type or degree of pigmentation.