['Not all health care workers (HCWs) are at the same risk for tuberculin skin test (TST) conversion, indicating latent tuberculosis (TB) infection.', 'To identify risk factors for TST conversion among HCWs.', 'A retrospective cohort study conducted at a tertiary university medical centre included every HCW who had had a negative two-step TST at work entry and at least one consecutive TST in the period 2005-2009 (mean follow-up period 55 months). Binomic logistic regression analysis was used to identify risk factors for TST conversion. Potential risk factors such as age, health care profession, patient exposure profile, workplace division and history of bacille Calmette-Guérin vaccination were entered in the model.', 'A total of 450 subjects met the inclusion criteria, of whom 93 had TST conversion. The highest annual rates of TST conversion occurred in workers who worked as housekeeping staff (6.9%). Older age, a work environment with high patient turnover and employment in maintenance departments were significant risk factors (adjusted odds ratios 2.05, 5.2 and 8.4 respectively).'] Do housekeeping health care workers have the highest risk for tuberculin skin test conversion?