We compared in rabbits the effects of laser iridotomy by either argon or neodymium (Nd):YAG laser on prostaglandin E2 (PGE2) production by the iris/ciliary body, its accumulation in the aqueous humor and the aqueous protein levels. PGE2 production by the iris/ciliary body, following exposure to argon or Nd:YAG laser, was similarly enhanced, with peak levels of 22.8 +/- 4.7 and 24.1 +/- 8.2 ng/mg, respectively. An increase in aqueous PGE2 levels was more pronounced in the argon as compared with the Nd:YAG group, with peak levels of 56.7 +/- 17.3 and 20.0 +/- 7.7 ng/ml, respectively. PGE2 production correlated well with aqueous PGE2 levels in the argon group, but not in the Nd:YAG group. Protein accumulated in the aqueous humor following irradiation by both types of laser light, with higher levels occurring in the argon group. These results are indicative of possible differences in the extent of the inflammatory reaction induced by the application of argon and Nd:YAG laser light to the iris.