Disseminated Leishmaniasis (DL) is an emerging and severe form of Leishmania (Viannia) braziliensis infection defined by the presence of 10 and up to more than 1,000 skin lesions and a high rate of mucosal involvement. DL has been associated with high rates of failure to antimony therapy. Often confused with diffuse cutaneous leishmaniasis (DCL), DL is considered clinically, immunologically and histopathologically distinct from DCL. While DCL patient’s exhibit poor lymphocyte proliferation and absent or low production of IFN-γ upon exposure to soluble leishmania antigen (SLA), an impaired Th1 immune response has not been documented in DL. The mechanisms underlying parasite dissemination remain unknown. Parasite factors are also known to influence the pathogenesis of leishmaniasis. As L. (V.) braziliensis is polymorphic, dissimilarity among strains has been associated with different clinical forms of disease, as well as failure to antimonial therapy. The participation of monocytes is also notable in host inflammatory response against CL, as the enhancement of intermediate monocytes provides an important source of TNF, a cytokine associated with tissue damage in tegumentary leishmaniasis. The Toll-like receptor (TLR) signaling pathway is a primary defense mechanism against infectious agents. The elevated expression of TLR2 and TLR4 by intermediate monocytes from L.(V.) braziliensis-infected CL patients in comparison to healthy subjects has been associated with TNF production. The present work compared the function of monocytes obtained from cutaneous leishmaniasis (CL) and DL patients in response to infection with isolates of L. braziliensis pertaining to both of these two clinical forms of disease. Mononuclear cells obtained from DL and CL patients were infected with different L. braziliensis isolates. Numbers of infected cells and parasite load were determined by microscopic evaluation of 100 monocytes following Romanowsky staining of cytocentrifuge preparations. Respiratory burst, TLR2 and TLR4 expression and cytokine production were evaluated by cytometry. DL isolates infected more monocytes, induced greater respiratory burst, higher expression of TLR2 and TLR4 and more cytokine production compared to isolates from CL patients regardless of the origin of monocytes used (DL or CL). However, greater parasite multiplication and higher TLR expression were seen in monocytes from DL patients compared to CL following infection with DL isolates. Our results indicate the participation of both parasite genotype and host factors in the pathogenesis of DL.