In a large series of senile cataract extractions, the incidence of flat anterior chamber (AC) that reformed spontaneously or responded to medical therapy was 5.9%. Most flat ACs in this group resulted from wound leaks or combined wound-leak and pupillary block mechanisms. Higher incidence of aphakic flat AC was present in patients with preexisting chronic simple glaucoma or angle-closure glaucoma as compared to nonglaucoma groups. Lower incidences of aphakic flat AC were found in eyes sutured with 7-0 silk or 7-0 catgut, eyes in which five sutures were placed, eyes in which chymotrypsin was not used, and eyes in which the cryoextractor was used. The final visual acuity and intraocular pressure of eyes in the aphakic flat AC treated medically did not differ from that of an uncomplicated aphakic population.