Occupational and environmental aluminum (Al) exposure cause serious health problems by interaction with biological systems. Al is one of the most documented metals because its cellular targets are unclear biochemical processes and membranes of organisms. The major aim of the present study was to investigate the alteration of serum and urine aluminum in occupational exposure and to observe whether the metal exposure could cause any changes in pteridine-pathway-related critical compounds such as urinary neopterin and biopterin and blood dihydropteridine reductase (DHPR). In this study, determination of the metal concentrations was carried out in Al-exposed workers (n=23) and healthy volunteers (n=18) by using atomic absorption spectrometer. DHPR enzyme activity and levels of neopterin and biopterin were detected by spectrophotometric and high-performance liquid chromatographic methods, respectively. It was found that occupational exposure to the metal led to a statistically significant increase in serum Al levels compared to the controls (p < 0.05). At the same time, urinary neopterin and biopterin concentrations of the exposed group were higher than nonexposed subjects (both p < 0.05). The correlations among Al levels and DHPR activity; magnesium concentration in serum and urine, working years, smoking status, and age were evaluated.