This study had for aim to describe the clinical aspects and favoring factors of mucosal Leishmaniasis in an Amazonian population of 30,000 habitants in Guajara-Mirim (Rondonia-Brazil).A descriptive study was made of 16 patients with mucosal Leishmaniasis among 170 patients infected by Leishmania. Inclusion criteria were a mucosal lesion and positivity of direct microscopic examination. The patients were investigated retrospectively.Patients with mucosal Leishmaniasis were young and mostly male The absence of treatment and the number of cutaneous lesions were probably responsible for the mucosal form, as well as the host immune response and maybe, the parasite species or vector characteristics.The mucosal form of leishmaniasis affects more often young male patients and this form must be detected early to avoid destructing lesions.