The Authors have analysed the histopathological alterations observed in 162 cases of Mucocutaneous Leishmaniasis from Três Braços, Bahia, of whom 131 (80,9%) had purely cutaneous lesions and 31 (19,1%) had only mucosal lesions. The clinical behavior of 5 histopathological forms was documented in relation to treatment. The best prognosis was associated with the exudative granulomatous histopathology, a phase where the a host mechanism to use the parasite is evident leading to necrosis and granuloma formation as a residual sign. Therapy in this phase merely hastened the process. In a further large group the lesions were classified as exudative cellular reaction (cutaneous forms), an exudative necrotic reaction and an exudative necrotic gra- nulomatous reaction. In these cases the mechanisms of host defense are still being developed and the effect of therapy is to reduce the time to healing. Cutaneous cases with an exudative tuberculoid reaction had a worse prognosis, although there was a favourable response to treatment if the patient was young, the lesion was of short duration and the intradermal leishmanin test was not exaggerated Lastly are a group of mucosal cases with an exudative cellular reaction where this infiltrate may be a manifestation of auto agression. These cases, also classified as exudative tuberculoid, occur in adult patients with longstanding lesions and an exaggerated leishmanin skin test. They have a poor prognosis. This study develops suggestions for a classification based on the histopathological picture which could be valuable in predicting prognosis and influencing the choice of treatment. This classification is strictly morphological and is easy for the pathologist to apply. It appears to, correspond to the clinical course of the illness and could aid the clinician in the initial case evaluation.