On the supposition that a predisposition towards TB in individuals is characterized by a need for affection and a life situation which frustrates or aggravates this need, it is postulated that large-scale threats to the interpersonal relationships in a nation or group will tend to increase the communal prevalence of TB. Threatened or broken love-links with an associated significantly increased incidence of pulmonary TB occur in war, in primitive cultures after the advent of the white man, involuntary or economically determined migrations, and in mental hospitals where the schizophrenic is particularly vulnerable to TB because of the nature of his mental disease which leads to the destruction or loss of natural affection.