Leishmanioses are a group of infections caused by the protozoa Leishmania. Humans are infected by female sandfly bites. Leishmaniosis is found in Mediterranean Europe, America, Africa and Asia. Various clinical expressions are possible: visceral (kala-azar) or cutaneous (Old world cutaneous leishmaniosis). In Mediterranean Europe, visceral leishmaniosis with the classical triad, splenomegaly, pallor, fever, was traditionally a childhood disease whereas today the disease with atypical clinical expressions strikes immunocompromised patients. In these atypical forms of visceral leishmaniosis, diagnosis and treatment are particularly difficult. Leishmania-DNA research using polymerase chain reaction is often necessary to perform the diagnosis, and lipid-associated formulations of amphotericin B, rapidly effective and well-tolerated in patients without immunodeficiency, do not prevent recurrences in immunocompromised patients.