The influence of posterior chamber lens implantation on the aqueous humor dynamics was investigated using anterior chamber fluorophotometry before and 9 weeks after cataract extraction and IOL implantation. Thirty-four patients finished the protocol. Patients with preexisting glaucoma or those having a history of ocular or systemic inflammation were excluded from the study, as were those taking topical or systemic drugs with potential influence on the aqueous humor dynamics. Nine weeks after IOL implantation a mean increase in aqueous humor flow was noted. This increase was highly significant (p less than 0.01, Student's paired t-test). There were no significant changes in aqueous humor dynamics in the unoperated fellow eyes which served as controls. The significant difference in aqueous humor flow 9 weeks after cataract extraction and IOL implantation indicates that the liberation of prostaglandins may cause an increase in the ease of outflow facility.