Background: The aim of this study was to compare serum neopterin levels in patients with active pulmonary tuberculosis, healthy healthcare workers who had close contact with patients, and healthy volunteers. All of the healthy volunteers stated that they had not encountered possible risk factors for exposure to Mycobacterium tuberculosis infection. Material/Methods: Thirty-nine patients, 39 healthy healthcare workers, and a control group of 39 healthy volunteers who had no infection or other diseases were included in this study. Neopterin assay was performed in accordance with the manufacturer's instructions. Results: Serum neopterin levels were 18.6±14.2 nmol/l in patients, 9.8±2.9 nmol/l in healthy healthcare workers, and 3.4±5.2 nmol/l in healthy volunteers. Serum neopterin levels in each group were significantly different from each other (p<0.01). Conclusions: Levels of neopterin in patients and healthy healthcare workers significantly differ from the levels in healthy controls. The higher serum neopterin levels in healthy healthcare workers may be attributed to latent Mycobacterium tuberculosis infection, but it does not seem to be used in the diagnosis of latent Mycobacterium tuberculosis infection alone. However, more experiences are needed. © Med Sci Monit.