The purpose of this study was to investigate iron (Fe), zinc (Zn), and copper (Cu) levels of aqueous humor, lens, and serum in nondiabetics and diabetics and to determine the effects of diabetes on Fe, Zn, and Cu contents in the lens. Fe, Zn, and Cu contents of aqueous humor, lens, and serum samples of 19 patients (9 nondiabetic patients with a mean age of 62.3 5.4 yr, and 10 diabetic patients with a mean age of 59.5 5.9 yr) were analyzed by atomic absorption spectrometry using a prospective study design. The lens levels of Cu in diabetic patients were significantly higher compared with nondiabetic patients (p = 0.02); however; there was no difference in the other elements (Zn, Fe; p = 0.28, p = 0.74, respectively). The levels of Fe, Zn, and Cu in the aqueous humor and serum of diabetic patients were not found to be statistically significant when compared to nondiabetics (p = 0.46, p = 0.11, p = 0.18, and p = 0.22, p = 0.43, p = 0.72, respectively). These results demonstrate that increased Cu content of the lens presumably has a greater association with the development of lens opacification in diabetics than Zn and Fe content.