Senile macular degeneration (SMD) is a leading cause of legal blindness in western countries. The role of immunocompetent cells in the pathogenesis of this disease has not been widely recognised. In this work specimens were studied by electron microscopy to provide ultrastructural details of the role of immunocompetent cells in early, intermediate and late stages of the disease. Additionally, we have analysed the frequency and distribution of inflammatory cellular infiltrates using wax histology. The results illustrate the involvement of macrophage-series cells, fibroblasts, lymphocytes and mast cells in neovascularisation, atrophy of the retinal pigment epithelium and the breakdown of Bruch's membrane. These observations, together with previous clinicopathological studies, have led us to suggest that SMD has a chronic inflammatory component.