Attention is drawn to illness semantics and the need to move beyond health social science research on discrete diseases to sets of illnesses perceived to be interrelated within popular health culture. Considered is the weak lungs/TB complex as it is conceptualized in relation to other types of lung disease as well as predisposing factors which influence the moral identity of the afflicted and the social relations of illness. The illness category weak lungs is broad and covers a variety of symptom states inclusive of TB. While some people equate weak lungs with TB, many others think of weak lungs as a condition which may develop into TB over time. TB is recognized to be contagious, but many people do not perceive weak lungs to be contagious. Treatment practice is discussed in relation to perceptions of illness severity, economics, expectations from medicines and coexisting health concerns. Faith in biomedicine is strong. Broad usage of the term weak lungs affects self-treatment practices and over-the-counter purchase of TB medications. Several TB medicines are labeled in such a way as to give the impression that they are vitamins for the lungs. This association leads people to think that the medication is useful for all illnesses which weaken the lungs, even if taken for a short duration. Attention is drawn to the manner in which inappropriate use of TB medication increases the chances of drug resistance. Data presented on TB drug resistance in the Philippines suggests why a consideration of illness semantics is important.