A survey of 26 eye pathology laboratories for a five-year period ending in 1980 disclosed that sympathetic ophthalmia occurred in two of every 1,000 eyes examined. Of the 53 eyes with sympathetic ophthalmia, 29 (55%) had posttraumatic and 24 (45%) had postsurgical sympathetic ophthalmia. Ten of the 53 eyes (19%) had undergone one or more operations that included vitrectomy. Sympathetic ophthalmia developed after surgery in eight of the ten eyes and after accidental trauma in the other two. A survey of 34 retinal surgeons who had done 14,915 vitrectomies (10,000 of which were estimated to have been done in eyes with no other penetrating wound) disclosed that sympathetic ophthalmia occurred in nine patients (an incidence of 0.06%). In one of these, the only operative procedure and penetrating wound was a vitrectomy (an incidence of 0.01%). The risk of sympathetic ophthalmia after a vitrectomy alone in an eye without a previous penetrating wound is approximately the same as that for other surgical procedures involving penetration of the uveal tract. The risk increases if vitrectomy is accompanied by accidental penetrating wounds or other surgical procedures.