Residual glaucoma after an iridectomy in primary angle-closure glaucoma, or so called post-iridectomy glaucoma, is rather well recognized recently. It is also realized that probably different mechanisms in addition to the pupillary block mechanism co-exist in the same glaucoma eye. The efficacy of medical treatment for such glaucoma was evaluated by dark prone provocative test after timolol or pilocarpine topical instillation to compare with non-medication as control in 72 iridectomized eyes. The results revealed pilocarpine medication has only six eyes positive (8.3%) and significantly prevents IOP elevation in the test while timolol has no significant effect (23 eyes positive, 31.9%) when both were compared with the control study (31 eyes positive, 43.1%). The results may also suggest additional different mechanisms involved in this glaucoma.