As part of a multifactorial study of the causes of breakdown to active tuberculosis of inactive pulmonary lesions, HLA-A, -B, and -DR typing was performed on 256 Hong Kong Chinese patients and 100 healthy control subjects. Patients were classified into those with smear-positive, active pulmonary tuberculosis (n = 103), those with inactive disease (n = 113), and those with breakdown to active disease after 6 months or more of inactivity (n = 40). Separately, 21 multiple-case families comprising 38 available parents and 93 offspring were examined for HLA haplotype segregation in relation to infection. Results of both studies indicate that among Hong Kong Chinese there is no statistically significant association between HLA and susceptibility to pulmonary tuberculosis.