The kinetoplastidae are flagellated protozoans that are widely distributed in nature and cause diseases in both plants and vertebrates. They are distinguished by presence of kinetoplast, that is, the DNA-containing region in their single large mitochondrion. The diseases in crops and lifestocks cause considerable economic loss while serious human suffering and death occur in infections in man. In humans, the diseases include trypanosomiasis, leishmaniasis and chagasis. Trypanosomiasis is caused by infection with two of the three subspecies of Trypanosoma brucei; Chagas disease is caused by infection with Trypanosoma cruzi and various forms of leishmaniasis are caused by different species of Leishmania. These forms of diseases have been classified by the World Health Organization (WHO) as major tropical diseases. According to WHO estimates, about 12 million people suffer from the disease but close to 350 million people in 80 countries world-wide are at risk (Anon, 1990). They are endemic in tropics, subtropics and southern Europe in settings ranging from rain forests in the Americas to deserts in Asia and Middle East. The cellular biology of these kinetoplastids is essentially similar, for example, they are all motile protozoans with a single flagellum that originates close to their large single mitochondrion. They all have glycosomes, that is, micro-bodies that perform glycolysis. All typically grow asexually although sexual recombination has been shown or inferred but is not obligate in any one of them. They divide by binary fission during which their nucleus does not undergo membrane dissolution or chromosome condensation. They are well adapted to their hosts and evade immune elimination by antigenic variation, and alteration of immune responsiveness. There is no effective immune response against human trypanosomiasis which invariably results in fatality. In the case of T. cruzi and Leishmania spp., the immune response tends to control rather than eliminate them. Leishmaniases constitute a broad spectrum of diseases, including the localized cutaneous and the disseminated visceral and mucocutaneous forms. Cutaneous and mucosal leishmaniases cause chronic skin sores and facial disfigurement respectively while untreated