Objectives: Occupational lead (Pb) exposure is still an important health problem in the world. Longterm Pb exposure causes several adverse effects. The aim of this study was to investigate the changes of inflammation markers with chronic Pb exposure by analyzing neopterin levels and kynurenine (Kyn) to tryptophan (Trp) ratio that reflects indolamine 2,3-dioxygenase activity and to compare with healthy volunteers' parameters. Methods: Blood lead levels (BLLs) were analyzed by atomic absorption spectrometry. Urinary neopterin and serum Kyn and Trp levels were analyzed by highperformance liquid chromatography. Results: According to our results, mean BLL of the 29 workers was 20.4 +/- 9.6 mu g/dl. Urinary neopterin levels, serum Kyn levels, and Kyn/Trp of Pb workers (188 +/- 52 mu mol/mol creatinine, 2.70 +/- 0.66 mu M, and 43.19 +/- 10.38 mu mol/mmol, respectively) were significantly higher than controls (144 +/- 35 mu mol/mol creatinine, 2.08 +/- 0.34 mu M, and 32.24 +/- 7.69 ae mol/mmol, respectively). Pb-exposed workers were divided into further three groups according to their BLLs: as 10-19 mu g/dl (n=18), 20-29 mu g/dl (n=8), and 30-49 mu g/dl (n=3). Neopterin levels of the workers with BLL of 30-49 mu g/dl were significantly higher than those of BLL with 1029 mu g/dl, while Trp levels decreased. Kyn/Trp of workers with BLL of 30-49 mu g/dl were elevated significantly compared with the workers with BLL<30 mu g/dl. In addition to neopterin, Kyn and Kyn/Trp levels were positively influenced by Pb exposure. Conclusions: Increased level of inflammation markers confirms the adverse effects of Pb even low BLLs, and we suggest that monitoring BLLs with inflammation markers could help to prevent serious occupational health problems.