The study was conducted among 92 male workers, divided into two groups depending on workplace and level of inorganic dust containing free crystalline SiO2 in the work environment, and 43 healthy workers without exposure to dust aerosols. The measured inhalable and respirable dust concentrations, as well as the concentration of free crystalline silica (FCS) in the respirable fraction were different for the two groups, but the percentage of free crystalline silica in the respirable fraction was almost identical. Significantly higher neopterin levels were found in workers exposed to dust, compared to the control group: 12.72 nmol/L and 6.32 nmol/L respectively (p<0.05). No significant difference was found between serum neopterin levels in both groups of the exposed workers. Among the groups with different length of service, a statistically higher neopterin level was evident only in the workers with length of service less than 10 years (p<0.05). The correlation analysis did not find a significant dependence of neopterin levels on the age of the studied workers or on the duration of smoking in packet years. The difference between neopterin levels in smokers and non-smokers was nonsignificant. The results obtained show that increased neopterin levels in the exposed workers are not influenced by individual features, duration and level of exposure to inorganic dust, but mostly by the presence of FCS in the respirable fraction.