Following needling and aspiration of cataract, the anterior chamber aspirate from 28 eyes of 23 patients was analyzed cytologically. The almost purely macrophagic cellular response was directly related to the time elapsed between needling and aspiration. The type of cell was identical to but much fewer in number than cells seen with phacolytic glaucoma. The escaping lens protein of senile hypermature cataracts is probably altered and more noxious than the "normal" lens substance found in the anterior chamber following needling of soft cataracts. No difference in cellular response was noted between those eyes from 15 patients who had had no previous surgical manipulation of the lens in the fellow eye and 13 who had experienced such surgery. Phacoanaphylactic endophthalmitis must involve factors (such as the genetic makeup of the individual) other than simply the presence of altered lens protein within the eye following disruption of the lens capsule.