The argon laser beams' effect on angle structures was studied in 20 uncontrolled glaucomatous eyes. Nineteen eyes became hypotensive quickly, but in 15, the elevated tension returned during the 20 to 40 day follow-up period. Four eyes sustained low pressures throughout the ten-month follow-up period. Two were of babies with congenital glaucoma, one had simple glaucoma following an unsuccessful filtering operation, and one was aphakic following congenital cataract extraction. Ten eyes were medically controlled postoperatively, and six were failures that had to undergo further surgery. Outflow facility measurements revealed an increase in C values during the hypotensive period. The C values were reduced later, with the decrease corresponding to the increase in intraocular pressures. The hypotensive effect together with the increase in outflow facility was probably related to laser-induced openings in the angle structures. The varying results at the later stages depended on whether or not these openings remained opened, or became partially or completely closed during healing.