Introduction: Visceral leishmaniasis (VL) and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/ AIDS) co-infection has been a research topic of interest worldwide. In Brazil, it has been observed that there is a relative underreporting and failure in the understanding and management of this important association. The aim of this study was to analyze epidemiological and clinical aspects of patients with VL with and without HIV/AIDS. Methods: We conducted an observational and analytical study of patients with VL followed in a Reference Service in the State of Maranhão, Brazil from 2007-2013. Results: In total 126 patients were enrolled, of which 61 (48.4%) were co-infected with HIV/AIDS. There were more males among those with HIV/AIDS (85.2%, P>0.05) or with VL only (81.5%, P>0.05). These findings significantly differed based on age group (P<0.003); the majority of patients were aged 31-40 years (41.0%) and 21-30 years (32.3%) among those with and without HIV/AIDS co-infection, respectively. The incidence of diarrhea and splenomegaly significantly differed between the two groups (P=0.0014 and P=0.019, respectively). The myelogram parasitic examination was used most frequently among those with HIV/AIDS (91.8%), followed by those with VL only (69.2%). VL recurrences and mortality were significantly higher in the HIV/AIDS co-infected patients (P<0.0001 and P=0.012, respectively). Conclusions: Patients with VL with or without HIV/AIDS co-infection were mostly adult men. Diarrhea was more frequent in HIV/AIDS co-infected patients, whereas splenomegaly was more common in patients with VL only. In the group of HIV/AIDS co-infected patients, there was a higher rate of VL recurrence and mortality.