The YAG (yttrium aluminum garnet) laser has been recommended for anterior capsulotomies. One major complication is elevated intraocular pressure. We report a study of the biochemical content of the aqueous humor after a YAG laser anterior capsulotomy. We analyzed 6-keto-prostaglandin F1 alpha, thromboxane B2 and protein concentrations in the aqueous humor of human eyes. The average values of protein, 6-keto-prostaglandin F1 alpha, and thromboxane B2 in the control eyes were 81.3 +/- 14.0 mg/dL, 17 +/- 30 pg/mL, and 10 +/- 10 pg/mL, respectively. These values were elevated to 182.4 +/- 81.3 mg/dL, 401 +/- 55 pg/mL, and 576 +/- 148 pg/mL, respectively, after YAG laser anterior capsulotomy. The samples with a moderate level of 6-keto-prostaglandin F1 alpha (less than 300 pg/mL) had negligible changes of thromboxane. The elevation of thromboxane was obvious only when prostaglandin levels rose above 300 pg/mL.