In recent years, textbooks and reviews on mechanisms involved in cellular immunity have emphasized that measles adversely influences tuberculous lesions. The medical literature was critically investigated for the basis of this claim. All field studies reviewed possessed strong deficiencies in the pertinent data and the methods of their collection. These deficiencies rendered invalid conclusions concerning the ability of measles to activate tuberculosis. Indirectly, there are also no adequate epidemiologic data to support the concept that measles suppresses tuberculous immunity when it suppresses tuberculin skin reactivity. Considering all the available information, one may conclude that if measles does have a deleterious influence on tuberculosis, it is probably at low frequency in most populations.