Twenty-eight patients with pseudotumor cerebri underwent 40 optic nerve sheath fenestrations for relief of visual loss or to preserve vision. Twenty women and eight men underwent 16 unilateral fenestrations and 12 bilateral operations. Papilledema disappeared or was strikingly reduced in 24 of 28 patients. The other four patients had gliotic discs (two patients) or were followed up for only a short time. Visual acuity improved in 12 of 40 eyes and remained the same in 22 of 40 eyes. Seventeen eyes had preoperative visual acuity of 20/30 or better. In six eyes visual acuity decreased. Of eight eyes operated on that had visual acuity of 20/200 or worse, only three showed improvement. Visual fields improved in 21 of 40 eyes and remained the same in ten eyes. Five of the ten eyes that did not change had poor vision before surgery. Eight eyes in five patients continued to lose acuity postoperatively. Each of these eight eyes had a concomitant loss of visual field. An additional two eyes developed visual field loss with preserved visual acuity. The indications for surgery are early evidence of progressive loss of visual field or acuity in a patient with pseudotumor cerebri. Severe vision loss presents little opportunity for improvement but fenestration may be used in a last effort to preserve or restore vision.