Transforming growth factor-β (TGF-β) is a molecule with an extremely wide range of biological activities. In aqueous humor (AH) TGF-β is one of the factors involved in immunosuppression, and contributes to the immunological privilege of the anterior chamber of the eye. It may well be that ocular diseases, like corneal inflammation, disturb this immunological privilege by altering the cytokine equilibrium in AH. We compared the amounts of active, total, and the ratio active/total TGF-β in AH of patients with severe corneal disease leading to corneal transplantation with those values in patients with cataract. IL-6 levels in AH were determined too since raised levels may indicate intraocular inflammation. The aqueous humor samples were collected from patients with cataract undergoing cataract surgery and patients with corneal disease undergoing corneal transplantation. TGF-β(2) levels and IL-6 levels in AH were measured with a capture ELISA. TGF-β(2) in AH was mainly present as a latent complex. Eyes with corneal disease prior to corneal transplantation did not differ from eyes with cataract in the level of active, total, or the ratio active/total TGF-β(2) in AH. None of the eyes showed significant IL-6 levels. In both corneal disease and cataract the amounts of IL-6 and TGF-β(2) in AH thus suggest the presence of a normal immunological balance. This may have a positive influence on corneal graft survival. However, we observed raised levels of active TGF-β(2) in age-group 61-80 years, which might be related to the onset of cataract development.