One of the main aspects related to non-adherence to combined antiretroviral therapy (cART) for patients infected with the Human Immunodeficiency Virus (HIV) refers to the abandonment of outpatient care. This study was aimed to estimate the loss to follow-up in outpatient HIV care at a Regional Referral Clinic (SAE) for HIV/AIDS in the city of Juiz de Fora, Brazil, and to identify associated factors and predictors. This is a prospective cohort of patients older than 18 years, under cART and regular outpatient care. The study included patients who attended medical visits during July-August 2011. Those who did not return to the clinic for new medical appointments within 90 days after the sixth month of follow up were considered lost to follow-up in outpatient care. Variables with P value ≤0.25 in the univariate analysis were included in a logistic regression model, adopting a significance level of 0.05. Among the 250 patients included in the study, 44 (17.6 %) were lost to follow up in outpatient care. Among these, 38 (86.4 %) were located in the cART delivery database system (SICLOM). Younger patients (≤43 versus >43 years) (OR 2.30 CI 1.06-5.00, P = 0.04), and patients attended by physician "E", when compared with physicians "A", "B", "C" or "D" (OR 5.90 CI 2.64-13.18, P = 0.00) were more likely to be lost to follow-up. Patients admitted in the service for 7 years or more were also more likely to be to lost to follow-up (OR 2.27 CI 1.2-4.4, P = 0.01), although this association did not remain statistically significant in the multivariate analysis. Although the purpose of the study, to identify individual factors associated to loss to follow-up, positives associations with a specific physician and with patients admitted in the service for 7 years or more suggest organizational factors. Although the majority of patients lost to follow-up in outpatient care were detected by SICLOM, a detectable viral load in most of these patients suggest a quality of outpatient HIV care proved ineffective, despite the availability of cART. We conclude on the need for further studies to investigate structural factors associated to loss to follow-up when enhanced retention strategies should be implemented in order to maintain an effective outpatient HIV care.