Senile disciform macular degeneration (SMD) is a neovascular/exudative form of age-related macular degeneration (AMD). In this study 340 eyes were followed up to assess the progression of SMD. The 340 eyes consisted of two groups. Group 1 was composed of 157 eyes with age-related macular changes other than choroidal neovascular membrane. Group 2 was made up of the contralateral eyes of 183 unilateral SMD eyes. Average ages were 61 and 64 in groups 1 and 2, respectively, and respective follow-up periods were 44 and 52 months. Choroidal neovascular membrane developed in 12 eyes in group 1 (7.6%) and in 19 eyes in group 2 (10.4%), a total of 31 eyes (9.1%). Retinal pigment epithelium (RPE) detachment was found as a predisposing lesion in 25 of these 31 eyes. Choroidal neovascular membrane developed in 12 of the 24 eyes with large RPE detachments. In 3 eyes neovascular membrane developed from an RPE detachment which had evolved from soft drusen. There were 3 eyes among the 62 eyes with soft drusen in which neovascular membrane developed directly from soft drusen. Based on these results, we classified AMD into 3 types; 1) atrophic, 2) predisciform, which includes RPE detachment and soft drusen, and 3) SMD.