In 67 eyes of 46 patients with chronic primary angle closure glaucoma, the effect of peripheral iridectomy in lowering the intraocular pressure was investigated retrospectively. In the majority of cases the pressure was reduced. For the whole population the mean reduction was 3.9 mmHg (SD 6.7 mmHg). The presence or extent of peripheral anterior synechiae showed no significant correlation with the amount of pressure reduction. A peripheral iridectomy is still recommended as first step in the treatment of primary angle closure glaucoma.