The results of argon laser trabeculoplasty (ALT) in a series of 252 patients are presented with follow-up of up to five years. The procedure is effective in chronic open-angle glaucoma (COAG), ocular hypertension and pseudoexfoliative (PXF) glaucoma. Most cases were treated initially over 180 degrees of the angle and repeat treatment of the remaining 180 degrees usually resulted in an additional fall in IOP which was maintained at two, three and four year follow-up with only a small number of these retreated cases having no fall on later follow-up. ALT was not very effective in further lowering IOP in eyes with IOP controlled to a low level before treatment or in low tension glaucoma. It was effective in most of a number of miscellaneous glaucomas including pigmentary glaucoma. Apart from the immediate high rise in IOP the main complication was a late high rise in IOP which was serious in degree and appeared mainly in PXF but also in two cases of ocular hypertension. The presence of a concomitant fall in IOP in the fellow untreated eye is important and probably due to better compliance with treatment. Almost all cases required medical treatment for glaucoma which could not be ceased after ALT. ALT should be seen as an adjunct to, but not a substitute for, medical treatment.