Treatment default is one of the most important factors that reduce the efficiency of tuberculosis therapy and its causes are associated with factors related to patient, drugs and health system. In Chile, default rate has remained around 7%, despite the different strategies implemented for its prevention. This study corresponds to the analysis of audits performed in cases of default and seeks to define a profile of these patients and determine the main causes that influence this result. Methodology: Descriptive study of the information contained in the audits sent between 2009 and 2013. Results: 134 audits were analyzed. Activity compliance was 35.9% and an incomplete record was observed in most cases. Most patients were male, between 15 and 45 years old and 91% was their first episode of tuberculosis. 62.7% had some risk factor associated with default, especially alcohol and drug abuse and 16.5% were homeless. Most cases default during the intermittent treatment phase and the cause of abandonment was mainly associated with patient factors such as substance abuse, feeling well and job instability. Conclusion: These findings reinforce the importance of applying the score of treatment default risk in patients entering treatment to establish strategies to prevent it.