Background: The non-adherence to tuberculosis treatment is associated with increased infection, antibiotic resistance, increased costs and death. Our objective was to identify factors associated with lack of completion of conventional treatment for tuberculosis in Peru. Patients and methods: An unmatched case-control study in patients diagnosed with tuberculosis from 2004-2005 who completed treatment until September 2006. The cases were defined as patients who discontinued treatment for ≥30 consecutive days, while the controls were defined as those who completed treatment without interruption. The factors were identified by logistic regression, calculating odds ratios (OR) and 95% confidence intervals (CI). Results: We studied 265 cases and 605 controls. The non-adherence to treatment in our study was associated with the male sex (OR. = 1.62; CI: 1.07-2.44), having felt discomfort during treatment (OR. = 1.76; CI: 1.19-2.62), a prior history of non-compliance (OR. = 7.95; CI: 4.76-13.27) and illegal drug use (OR. = 3.74; CI: 1.25-11.14). Also, if we consider the interaction of previous non-adherence history and poverty, the risk of non-completion increases (OR. = 11.24; CI: 4-31.62). Conversely, having been properly informed about the disease (OR. = 0.25; CI: 0.07-0.94) and being able to access health-care services within office hours (8. am-8. pm) (OR. = 0.52; CI: 0.31-0.87) were associated with better adherence. Conclusions: The non-compliance with anti-tuberculosis treatment was associated with non-modifiable factors (male sex, previous non-compliance) and with others whose control would improve compliance (malaise during treatment, illegal drug use and poverty). Likewise, providing access to the health-care system and improving the information given about tuberculosis should be priorities. © 2011 SEPAR.