La no adherencia parece ser motivo para el fracaso de los tratamientos. Investigaciones previas sobre el abandono del tratamiento para tuberculosis han identificado como factores de riesgo: falta de comunicacion medico-paciente, desorganizacion del servicio de salud, la indole del tratamiento, sentir mejoria de los sintomas, raza, consumo de alcohol y de drogas ilicitas. Este estudio tiene como proposito establecer la asociacion entre factores de riesgo y abandono del TAES en Medellin, entre enero de 2000 y junio de 2001. Se realizo un estudio analitico observacional de ;Casos y Controles;. Casos fueron los pacientes que iniciaron TAES en Medellin durante el periodo indicado y suspendieron el tratamiento por un mes o mas; los controles fueron pacientes que culminaron el tratamiento, tomados en razon de 1:3. Se encontro asociado al abandono del tratamiento: consumo de alcohol durante el tratamiento, tener otro vicio y tener dificultades para ir al centro de salud. En el limite de la asociacion se encontro el no tener capacidad de pago. En conclusion debe seguirse rigurosamente a los pacientes del programa de TB, mediante llamadas o visitas, para mantener un vinculo permanente con el personal de salud y reducir el riesgo de abandono. SUMMARY Non adherence seems to be a reason for the failure of the treatments. Previous investigations in tuber­culosis, have identified as risk factors associated with the abandonment: lack of communication doctor-patient, organization of health service, nature of treatment, sensation of improvement, race, and consumption of alcohol and illicit drugs. The pur­pose of this study was, to establish the association between Risk Factors and abandonment of DOTS in Medellin, between January of 2000 and June of 2001. A study Analytic Observational Case-Control Study was performed. Cases were the patients who be­gan DOTS in Medellin, during the mentioned pe­riod and who suspended the treatment for one month or more, and Controls were the patients who culminated the treatment, taken in reason 1:3. It was associated with non compliance: consumption of alcohol during the treatment, have another bad habit and have difficulties to go to the center of health. Just by the threshold of the association was found the lack of payment capacity of the patients. In conclusion, the patients of the program of TB should be followed rigorously, by phone calls or visits, to maintain a permanent bond with the health per­ sonnel and to reduce the risk of abandonment.