In an attempt to compare surgical peripheral iridectomy and laser iridotomy with regards to the long-term control of the intraocular pressure (IOP), analyses were carried out of the clinical records of 195 eyes of 149 primary angle-closure glaucoma patients who had undergone either peripheral iridectomy or laser iridotomy and were followed up for at least one year. One hundred and ten eyes underwent peripheral iridectomy and 85 eyes had laser iridotomy. The postoperative IOP not exceeding 20 mmHg was taken as the criterion for success. The iridectomized eyes showed no significant difference from those treated with laser iridotomy in 13 clinical factors, including age at treatment, sex, type of angle-closure glaucoma, preoperative mean IOP with medication, visual field, extent of peripheral anterior synechiae (PAS) and horizontal cup/disk (C/D) ratio. The rate of successful IOP control was obtained in 76.4% of the eyes in the peripheral iridectomy group and in 75.3% of the eyes in the laser iridotomy group. It appears that laser iridotomy is just as effective as surgical iridectomy in normalizing IOP. Discriminant analysis was done to derive a discriminant function consisting of a set of factors that will prognosticate the response of primary angle-closure glaucoma either to surgical iridectomy or to laser iridotomy. Four factors were demonstrated to be significant prognosticators. They were preoperative mean IOP with medication, visual field change, C/D ratio and PAS-index, in order of statistical significance. The discriminant function yielded the discriminant efficacy of 71.2% in overall cases.