Leaving Against Medical Advice has harmful consequences for public health, the patient and the medical economy, being this an unpublished topic in drug abusers hospitalized due to acute health problems. Our objective was to identify the incidence of leaving the hospital AMA and related re-admisssions, the characteristics of patients leaving AMA, and the opinion of the patients and the professionals about related risk factors. We designed an observational, prospective and analytic study of active drug abusers being admitted into an infectious diseases ward. Patients were interviewed about the hospital conditions that may induce leaving AMA. The clinical and social characteristics of the patient were also registered. When a patient left AMA, he was asked about the reasons that prompted him or her to leave. The nurse was also asked for his or her opinion. The incidence of leaving AMA was 15%. 54.5% of patients leaving AMA were readmitted into the hospital and 14% were diagnosed of tuberculosis. Statistical association was observed between leaving AMA and a deficiency in familiar and social support, taking more than two drugs, the consumption of alcohol, the use of heroin, the use of more than 2 types of drugs for the treatment of abstinence syndrome, neuroleptic treatment and previous episodes of leaving AMA. 64% of the patients were not satisfied with their abstinence syndrome treatment and this was reported as the main cause for leaving AMA in 40% of cases. Poverty and taking more than two drugs (mainly heroin) was strongly associated with drug abusers leaving AMA with acute health problems. The incidence of re-admissions showed that the patient was not cured when he or she left AMA, and this was related to a misuse of the medical resources.