As part of a plan to eliminate tuberculosis in America, tuberculin skin testing was advised for all US citizens, with isoniazid chemopreventive therapy administered to appropriate positive reactors. Implementation of this plan, however, may be limited by concerns over which skin test reactors should receive isoniazid therapy. Recent decision analyses suggest that, contrary to American Thoracic Society guidelines, asymptomatic skin test reactors under age 35 years with normal chest roentgenograms and no predisposing conditions to tuberculosis reactivation will not benefit from isoniazid chemopreventive therapy. Repeated analysis of these studies reveals that calculated life expectancy depends on estimates of the probability of certain chance outcomes. If the isoniazid-related hepatitis case-fatality rate is below 1%, isoniazid chemopreventive therapy appears to be beneficial. A literature review suggests that this rate is indeed this low. If the tuberculosis case-fatality rate is above 6.7%, also supported by the literature, the advantages of isoniazid therapy are further increased. This repeated analysis should reassure physicians that isoniazid chemoprophylaxis for tuberculin skin test reactors is beneficial to the individual and consonant with public health policies.