To determine the growth rate of subretinal neovascularization (SRNV) in age-related macular degeneration (ARMD), 35 pairs of serial fluorescein angiograms from 30 consecutive patients with SRNV who had not been treated with laser photocoagulation were analyzed. The daily growth rate of SRNV measured on consecutive fluorescein angiograms less than 120 days apart ranged from 0 to 74 microns (mean, 18 microns daily). The daily estimated growth rate of SRNV in any one direction ranged from 0 to 37 microns (mean, 9 microns daily). Documented initial slow growth of SRNV in one eye did not preclude a greater subsequent growth rate in the fellow eye. It was not possible to predict reliably the growth rate of SRNV. This reinforces the necessity of prompt evaluation of all subretinal neovascular membranes initially for the purpose of possible laser treatment.