This work describes the profile of patients with relapse after hospital detoxification at six months of outpatient follow-up. An observational and prospective study was carried out in patients with substancedependence disorder who were in the Detoxification Unit of the Vall d'Hebron University Hospital (Barcelona) between June 2009 and October 2010. Demographic, clinical, diagnostic and therapeutic variables were assessed. The criterion for relapse was a return to use of the substance that had led to hospitalization, and relapse was assessed by means of anamnesis, breathalyzer and/or urine analysis. Study variables were compared between patients who relapsed and those who did not. Of the 165 patients included, 108 patients finished the study (75% males, age 37.7 ± 9.5 years). A total of 72.2% had relapsed at the 6-month follow-up. Profile of patients who relapsed was: hospitalized for heroin detoxification (91.7% vs 8.3%, p = .038), polyconsumers (71.4% vs 32%, p = .05), high substance use in the hours prior to admission as a "farewell" (61.5% vs 39.5%, p = .04), patients with comorbidity (44.9% vs 23.3%, p = .04) and patients with affective disorders (19.5% vs 3.2%, p = .005). Detoxification from opiates and use in the hours prior to admission were associated independently with relapse at 6 months. There is a high percentage of relapses after hospital detoxification. Patients most likely to relapse are those dependent on opiates and those with compulsive use immediately prior to hospitalization.Key words: addiction, relapses, risk factors, in-patient unit, follow-up.El presente trabajo pretende comparar las características entre los pacientes que recaen en el consumo y los que se mantienen abstinentes, a los seis meses de seguimiento ambulatorio tras terminar una desintoxicación hospitalaria. Se realizó un estudio observacional y prospectivo en pacientes con trastorno por dependencia de sustancias que ingresaron en la Unidad Hospitalaria de Desintoxicación del Hospital Universitario de Vall d'Hebron desde junio 2009 hasta octubre 2010. Durante el ingreso se recogieron variables demográficas, clínicas, diagnósticas y terapéuticas, y se realizó la entrevista SCID. Se consideró recaída el reinicio del consumo de la sustancia que fue motivo de ingreso y se evaluó por anamnesis y alcohotest y/o urinoanálisis. Las variables de estudio se compararon entre los pacientes que recayeron y los que no. De 165 pacientes incluidos, 108 finalizaron el estudio (75% varones, edad 37,7±9,5 años). 72,2% recayeron a los 6 meses. El perfil de pacientes que recayeron fue: pacientes que ingresaban para desintoxicación de heroína (91,7% vs 8,3%, p = .038), policonsumidores (71,4% vs 32%, p = .05), pacientes que consumían horas previas al ingreso a modo de despedida (61,5% vs 39,5%, p = .04), aquellos con comorbilidad médica (44,9% vs 23,3%, p = .04), y con trastornos afectivos comórbidos (19,5% vs 3,2%, p = .005). La desintoxicación de opiáceos y el consumo en horas previas se asociaron de forma independiente con la recaída a los 6 mes...