We investigated the prevalence and predictors of positive tuberculin skin test (TST) results among prospective Vietnamese migrants. We interviewed and medically screened 1395 Vietnamese people aged over 15 years who had applied to migrate to Australia. Approximately 44% of applicants had an induration of 10 mm or more, and 18·6% had an induration of 15 mm or more. A positive tuberculin skin test at 5 mm, 10 mm and 15 mm of induration cut-points was significantly associated with age (OR 1·01–1·02 per year) and duration of smoking (OR 1·03–1·12 per year). Smoking appears to be an important factor associated with increased susceptibility to mycobacterial infection. It is not yet clear whether the increased tuberculin reactivity associated with smoking reflects an increased risk of tuberculosis among these migrants.