Results from the Macular Photocoagulation Study Group have shown that argon laser photocoagulation is beneficial in reducing the risk of severe visual loss in eyes with extrafoveal choroidal neovascular membranes secondary to senile macular degeneration (Senile Macular Degeneration Study or SMDS), ocular histoplasmosis (Ocular Histoplasmosis Study or OHS), or idiopathic neovascularization (Idiopathic Neovascularization Study or INVS). However, argon laser treatment has not been entirely successful in permanently eradicating active neovascularization from those eyes. Recurrent neovascularization in the form of either neovascularization contiguous with the treatment scar or independent neovascular membranes have been observed in 70 (59%) of the 119 SMDS eyes originally assigned to treatment, 40 (30%) of the 132 OHS eyes, and 11 (33%) of the 33 INVS eyes. Recurrence was accompanied by an increased frequency of severe visual loss. Characteristics of the patient, original lesion, and treatment were examined for their ability to predict recurrence. Cigarette smoking was related to the rate of recurrence in the SMDS (P = .02) and the INVS (P = .09). Younger age and female gender were associated with an increased frequency of recurrence in the OHS. Predictions of which eyes will suffer recurrence, however, cannot be made accurately. Therefore, careful follow-up of all treated eyes is indicated, particularly within the first year after initial argon photocoagulation.