The paper stresses the need for an interdisciplinary approach to the study of drug default among TB patients and presents several studies to discuss the role of motivation in reducing drug default, underscoring the importance of using an action-oriented definition of default. One study, conducted by the NTI, determined the number of defaults and the collection at which default occurred through a retrospective analysis of treatment cards. Analysis of the data collected from 2,419 patients showed that a large proportion of patients, whether they visited the (DTC - specialised institutions) or the Rural PHIs (GHIs), dropped out immediately after starting the treatment. Another study, on the influence of initial motivation, was conducted among adult patients newly diagnosed at the Bangalore LWTDTC. Three types of motivational contents for verbal communication were developed and a total of 407 patients were randomly distributed into three groups. The third study determined the influence of patient and family motivation on the drug collection of TB patients, using 250 newly diagnosed cases of TB at LWTDTC. It was concluded from the three studies that age, sex, education and occupation of the patients did not influence the drug collection pattern. Different schedules of motivation with variable quality of contents and, changed sequence of points did not appreciably affect the TB patients’ behaviour. Sputum-positive cases needed strong and more effective motivation compared to sputum-negative ones. Family motivation had a positive influence on the patients’ drug collection pattern.