The authors present a report on their experience with 10 patients with acute idiopathic blind spot enlargement. All had enlarged steep-margined blind spots without accompanying changes in optic disc appearance, significantly diminished visual acuity or color vision. Fluorescein angiography was obtained in eight patients. Five patients had retinal appearance that was either normal or could not be attributed to a known disease entity. Three patients had the multiple evanescent white dot syndrome, one had acute macular neuroretinopathy, and at least one had presumed ocular histoplasmosis. It has been proposed that acute idiopathic blind spot enlargement is a subset of multiple evanescent white dot syndrome. The authors' findings suggest that multiple evanescent white dot syndrome and other retinal diseases, some not yet identified, are subsets of acute idiopathic blind spot enlargement.