PURPOSE: To report the long-term outcome of intraocular pressure after laser peripheral iridotomy in Asian eyes with acute primary angle-closure. METHODS: Retrospective study of 111 eyes of 96 consecutive patients with acute primary angle-closure, presenting at the National University Hospital, Singapore, from 1990 to 1994. The presenting features of the affected eye and the treatment instituted were recorded. The subsequent long-term intraocular pressure outcome was analyzed. An increase in intraocular pressure on follow-up was defined as increase in intraocular pressure greater than 21 mm Hg and requiring treatment by medication or surgery. RESULTS: The mean follow-up period was 50.3 months (range, 9 to 107 months). The mean presenting intraocular pressure was 52.8 mm Hg (range, 28 to 80 mm Hg). One hundred ten eyes were treated with laser peripheral iridotomy, with resolution of the acute episode and intraocular pressure less than 21 mm Hg in all eyes after laser peripheral iridotomy. Of these, only 46 eyes (41.8%) were successfully treated with laser peripheral iridotomy alone in the long term. Sixty-four eyes (58.1%) developed an increase in intraocular pressure (requiring treatment) on follow-up, of which 49 eyes developed an increase in intraocular pressure within the first 6 months after acute primary angle-closure. Thirty-six eyes (32.7%) eventually underwent trabeculectomy because of uncontrolled intraocular pressure despite laser and medical therapy. CONCLUSIONS: In this study of Asian eyes, a high proportion (58.1%) of eyes with acute primary angle-closure developed an increase in intraocular pressure on long-term follow-up after resolution of the acute attack, despite the presence of a patent laser peripheral iridotomy. These results suggest a racial difference in the outcome of laser peripheral iridotomy after acute primary angle-closure in Asians, compared with Caucasians. Because a majority of eyes that develop an increase in intraocular pressure do so within the first 6 months of presentation, close monitoring of intraocular pressure is advised in the follow-up of patients with acute primary angle-closure.