To understand the role of prostaglandins F-2alpha, and E-2 in aqueous humor under the normal condition, their concentrations were measured by enzyme immunoassay in aqueous fluid obtained from either eye of 60 patients during cataract surgery and correlated with clinical factors as the age and intraocular pressure. The concentrations of prostaglandin F-2alpha in the aqueous of all patients were below the level of detection. The concentrations of prostaglandin E-2 in the aqueous were below the level of detection in 37 patients while ranged from 9 to 48 pg/mL (median, 31) in 23 patients. The levels of prostaglandin E-2 did not have correlation with the age of the patients or the intraocular pressure of the eyes. In conclusions, the concentrations of prostaglandin E-2 were apparently higher than the concentrations of prostaglandin F-2alpha in the aqueous. This study could not prove the relationship between prostaglandin levels and the intraocular pressure or the age.