The association between the aqueous humour levels of asymmetric dimethylarginine (ADMA) and pigment epithelium-derived factor (PEDF) was evaluated. Aqueous humour levels of ADMA and PEDF were measured by high-performance liquid chromatography and enzyme-linked immunosorbent assay, respectively, in 31 uveitis samples and nine cataract control samples. Aqueous humour ADMA and PEDF levels were significantly higher in infectious and non-infectious uveitis patients than in controls (0.67+/-0.04 nmol/ml and 0.55+/-0.03 nmol/ml versus 0.43+/-0.04 nmol/ml for ADMA; 8.22+/-1.45 microg/ml and 5.22+/-0.95 microg/ml versus 1.32+/-0.22 microg/ml for PEDF). A significant positive correlation between ADMA and PEDF levels in aqueous humour was found in control and uveitis patients. These results demonstrated that the aqueous humour level of ADMA is correlated with PEDF in humans and suggest that both ADMA and PEDF in aqueous humour may be elevated in response to inflammation in uveitis.