Laser iridotomy is a safe and effective treatment of pupillary-block glaucoma; however, increased intraocular pressure (IOP) may occur after the procedure. A flow cytometric study of aqueous humor was done 1.5 hours after neodymium: yttrium aluminum garnet laser iridotomy in 20 eyes. This sensitive and precise method did not reveal an apparent correlation between the degree of postoperative IOP spike and the amount of inflammatory cells or cellular debris induced by laser iridotomy. Although slit-lamp examination showed many "cells" in the anterior chamber in most after laser iridotomy, DNA histography found only scanty chromatin coating cells. We believe the so-called cells observed using slit-lamp biomicroscopy might not all be real cellular aggregates but rather aggregates of protein or fibrin in some situations.