Objective: The purpose of the study is to compare the results of vitreous surgery for a group of patients with chronic macular holes with a group of patients with acute-onset macular holes undergoing identical surgery. Design: A case-control study design was used. Participants: The duration of symptoms of visual loss due to macular holes was greater than 1 year's duration in 11 eyes in each group consecutively operated on within a few days. Intervention: All patients underwent macular hole surgery. Main Outcome Measures: Ophthalmoscopic resolution of the macular hole, improvement of 2 lines of visual acuity or greater, improvement in mean and median visual acuity, and rate of 20/40 or greater final visual acuity. Results: The hole resolved in 9 of 11 eyes in the chronic group and 10 of 11 eyes in the acute group. The mean (median) preoperative visual acuity was 20/151 (20/200) in the chronic group and 20/139 (20/200) in the acute group. The 3-month mean (median) postoperative visual acuity was 20/85 (20/80) in the chronic group and 20/62 (20/63) in the acute group. The final mean (median) postoperative visual acuity was 20/96 (20/ 100) in the chronic group and 20/48 (20/50) in the acute group (P = 0.022). The mean interval to final follow-up examination was 70 weeks for the chronic group and 44 weeks for the acute group. Five (45%) of 11 eyes with chronic holes and 8 (73%) of 11 eyes in the acute group had a final visual acuity of 2 lines or better than the preoperative visual acuity. Cataract extraction had been performed by the final follow-up examination in 7 chronic eyes (64%) and 2 acute eyes (18%). Conclusions: Chronic macular holes have a similar anatomic success rate, but a poorer visual prognosis than acute holes after macular hole surgery. Vitreous surgery benefits some patients with idiopathic macular holes of greater than 1 year's duration.