This chapter provides an updated overview of the relationship between leishmaniasis and AIDS, focusing on the past decade. It highlights the epidemiological, microbiological, pathogenetic, diagnostic, clinical, and therapeutic aspects of *Leishmania-HIV* coinfection. The chapter is divided into several sections, each addressing different regions and aspects of the coinfection. **Epidemiological Information:** - **Southern Europe:** The first case of *Leishmania-HIV* coinfection was reported in 1985, and the number of cases has increased rapidly. HAART has significantly reduced the incidence of coinfection in southern Europe, but the problem has expanded to other major foci of leishmaniasis. - **South Asia:** South Asia is the main focus for visceral leishmaniasis (VL), with India, Bangladesh, and Nepal being the most affected countries. The overlap of VL and HIV infections is significant, especially in areas like Humera, Ethiopia, where the rate of coinfection is high. - **Brazil:** Brazil is the epicenter of the HIV/AIDS epidemic in South America, and both CL and VL are increasing. The clinical forms of *Leishmania-HIV* coinfection in Brazil are different from those in southern Europe, with MCL being more common. - **Sub-Saharan Africa:** The chapter discusses the situation in countries such as Burkina Faso, Ethiopia, Kenya, Uganda, Somalia, and Sudan, highlighting the increasing prevalence of *Leishmania-HIV* coinfection and the challenges in managing it. **Microbiology:** - The chapter details the identification and typing of *Leishmania* strains in *Leishmania-HIV* coinfection cases, focusing on *Leishmania infantum* and other species. **Pathogenesis:** - The chapter explores the mechanisms by which the presence of both pathogens in the same host cell can enhance or influence the expression and multiplication of either pathogen. It discusses the impact of HIV on leishmaniasis and vice versa, including the induction of viral replication and disease progression by Leishmania. **Diagnosis:** - Various diagnostic methods for *Leishmania-HIV* coinfection are discussed, including parasitological, serological, antigen detection, and molecular techniques. **Clinical Aspects:** - The clinical manifestations of *Leishmania-HIV* coinfection are described, including VL-HIV coinfection, CL-HIV coinfection, and MCL-HIV coinfection. **Treatment:** - The chapter reviews the antileishmanial drugs and antiretroviral treatments used for *Leishmania-HIV* coinfection, emphasizing the challenges and complexities in managing these patients. Overall, the chapter provides a comprehensive review of the current state of *Leishmania-HIV* coinfection, highlighting the need for further research and improved management strategies.This chapter provides an updated overview of the relationship between leishmaniasis and AIDS, focusing on the past decade. It highlights the epidemiological, microbiological, pathogenetic, diagnostic, clinical, and therapeutic aspects of *Leishmania-HIV* coinfection. The chapter is divided into several sections, each addressing different regions and aspects of the coinfection. **Epidemiological Information:** - **Southern Europe:** The first case of *Leishmania-HIV* coinfection was reported in 1985, and the number of cases has increased rapidly. HAART has significantly reduced the incidence of coinfection in southern Europe, but the problem has expanded to other major foci of leishmaniasis. - **South Asia:** South Asia is the main focus for visceral leishmaniasis (VL), with India, Bangladesh, and Nepal being the most affected countries. The overlap of VL and HIV infections is significant, especially in areas like Humera, Ethiopia, where the rate of coinfection is high. - **Brazil:** Brazil is the epicenter of the HIV/AIDS epidemic in South America, and both CL and VL are increasing. The clinical forms of *Leishmania-HIV* coinfection in Brazil are different from those in southern Europe, with MCL being more common. - **Sub-Saharan Africa:** The chapter discusses the situation in countries such as Burkina Faso, Ethiopia, Kenya, Uganda, Somalia, and Sudan, highlighting the increasing prevalence of *Leishmania-HIV* coinfection and the challenges in managing it. **Microbiology:** - The chapter details the identification and typing of *Leishmania* strains in *Leishmania-HIV* coinfection cases, focusing on *Leishmania infantum* and other species. **Pathogenesis:** - The chapter explores the mechanisms by which the presence of both pathogens in the same host cell can enhance or influence the expression and multiplication of either pathogen. It discusses the impact of HIV on leishmaniasis and vice versa, including the induction of viral replication and disease progression by Leishmania. **Diagnosis:** - Various diagnostic methods for *Leishmania-HIV* coinfection are discussed, including parasitological, serological, antigen detection, and molecular techniques. **Clinical Aspects:** - The clinical manifestations of *Leishmania-HIV* coinfection are described, including VL-HIV coinfection, CL-HIV coinfection, and MCL-HIV coinfection. **Treatment:** - The chapter reviews the antileishmanial drugs and antiretroviral treatments used for *Leishmania-HIV* coinfection, emphasizing the challenges and complexities in managing these patients. Overall, the chapter provides a comprehensive review of the current state of *Leishmania-HIV* coinfection, highlighting the need for further research and improved management strategies.