Argon Laser Trabeculoplasty (ALT) have been used in the treatment of open angle glaucoma since 1982. During a five-year period, 1982-1986, the annual rate of glaucoma filtering operations has decreased steadily from 65 to 8. The pressure reducing effect is good both in simple and capsular glaucoma. In secondary glaucoma ALT failed to control the intraocular pressure in about 50%. Simple and capsular glaucoma respond well to repeated ALT, but in secondary glaucoma repeated ALT seems to be useless.