Health care workers (HCWs) are at risk for developing active tuberculosis (TB). The prevalence of latent tuberculosis infection (LTBI) in this group is unknown in Poland, due largely to the problems associated with the interpretation of the tuberculin skin test (TST) in BCG immunized population. The goal of the present study was to assess the prevalence of LTBI in both clinical and non-clinical 155 HCWs (120 females and 35 males) and to compare the groups at different levels of risk. All participants were interviewed using a questionnaire and underwent interferon-gamma whole blood assay (Quantiferon-Tb-Gold) (QTF) and TST. The questionnaire provided information on possible risk factors for LTBI, including demographic and socioeconomic details, the presence of BCG scars, and the degree of occupational exposure. We found that the prevalence of LTBI among HCWs was, on average, 27.1%. A higher risk of acquiring LTBI was associated with certain work locations (TB lab workers--prevalence 50%, TB ward clinicians--34%, nurses--30%). The prevalence in analytical lab technicians was 20%, in administration staff was 15%. The HCWs with positive QTF test results were older and worked longer than those who had negative results. There was a significant correlation between the level of IFN-gamma and both age (P<0.001) and length of employment (P<0.01). The correlation between the diameter of skin test induration and the magnitude of the INF-gamma response also was significant (P<0.001). We conclude that HCWs are at increased risk of infection, suggesting that appropriate preventive strategies should be undertaken. IFN-gamma test is a useful tool in detecting LTBI cases in a country where BCG vaccination is a national policy.